docs: 3.9 release notes (gatsbyjs#32206)

* placeholder for 3.9 release notes

* Update index.md

* Update with SSR support

* Update index.md

* update release notes

Co-authored-by: Lennart <[email protected]>
Co-authored-by: Ward Peeters <[email protected]>

docs/docs/reference/release-notes/v3.9/index.md

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+---
+date: "2021-07-06"
+version: "3.9.0"
+title: "v3.9 Release Notes"
+---
+
+Welcome to `[email protected]` release (July 2021 #1)
+
+Key highlights of this release:
+
+- [React 18 - New Suspense SSR Architecture](#react-18---new-suspense-ssr-architecture) - Enables SSR support for Suspense when using React 18 (Alpha)
+- [Shopify App for Gatsby Cloud](#shopify-app-for-gatsby-cloud)
+- [gatsby-source-contentful](#quality-of-life-improvements-to-gatsby-source-contentful) - quality of life improvements
+
+Also check out [notable bugfixes](#notable-bugfixes--improvements).
+
+**Bleeding Edge:** Want to try new features as soon as possible? Install `gatsby@next` and let us know
+if you have any [issues](https://github.com/gatsbyjs/gatsby/issues).
+
+[Previous release notes](/docs/reference/release-notes/v3.8)
+
+[Full changelog](https://github.com/gatsbyjs/gatsby/compare/[email protected]@3.9.0)
+
+---
+
+## React 18 - New Suspense SSR Architecture
+
+We're happy to announce support for the new React 18 server architecture during build time.
+When installing `react@alpha` and `react-dom@alpha`, you automatically opt into the new
+[`pipeToNodeWritable`](https://github.com/reactwg/react-18/discussions/37) renderer.
+Now you're able to use `Suspense` and `React.lazy` on the server as well.
+
+## Shopify app for Gatsby Cloud
+
+Following the brand-new Shopify source plugin published in the [previous release](/docs/reference/release-notes/v3.8/#gatsby-source-shopify-v5),
+this release brings Gatsby Cloud to Shopify App Store.
+
+Install Gatsby Cloud from the app store to quickly connect your Shopify store. Choose an existing project you’ve
+been working on or get up and running the Shopify starter in seconds.
+
+[Read more in our blog](https://www.gatsbyjs.com/blog/build-your-next-storefront-with-gatsby-cloud).
+
+## Quality of life improvements to `gatsby-source-contentful`
+
+- Don't ignore errors thrown when fetching assets via [PR #24288](https://github.com/gatsbyjs/gatsby/pull/24288)
+- Re-enable support for gif images via [PR #31986](https://github.com/gatsbyjs/gatsby/pull/31986)
+- Force base64 previews to be formatted as JPEG via [PR #32155](https://github.com/gatsbyjs/gatsby/pull/32155)
+
+## Notable bugfixes & improvements
+
+- `gatsby`: Bumped `express-graphql` to `0.12.0` to only have graphql v15 installed via [PR #31178](https://github.com/gatsbyjs/gatsby/pull/31178)
+- `gatsby`: Prevent generation of polyfill bundle if not needed via [PR #31993](https://github.com/gatsbyjs/gatsby/pull/31993)
+- `gatsby-plugin-netlify-cms`: Limit global styles to preview pane only via [PR #32106](https://github.com/gatsbyjs/gatsby/pull/32106)
+- `gatsby`: Add activity for writing out `page-data.json` files via [PR #31987](https://github.com/gatsbyjs/gatsby/pull/31987)
+- `gatsby`: Fixed a bug in develop when a new page is not available with HMR via [PR #32189](https://github.com/gatsbyjs/gatsby/pull/32189)
+- `gatsby`: Fixed a bug with filtering by custom interface fields (affecting WordPress plugin) via [PR #32195](https://github.com/gatsbyjs/gatsby/pull/32195)
+- `gatsby`: Performance improvements to queries with `limit`/`skip` via [PR #32135](https://github.com/gatsbyjs/gatsby/pull/32135)
+
+## Contributors
+
+A big **Thank You** to [our community who contributed](https://github.com/gatsbyjs/gatsby/compare/[email protected]@3.9.0) to this release 💜
+
+- [MichaelDeBoey](https://github.com/MichaelDeBoey): chore: Delete profile.js [PR #31997](https://github.com/gatsbyjs/gatsby/pull/31997)
+- [shanekenney](https://github.com/shanekenney): fix(gatsby-source-contentful): Don't ignore errors thrown when fetching assets [PR #24288](https://github.com/gatsbyjs/gatsby/pull/24288)
+- [axe312ger](https://github.com/axe312ger)
+
+  - fix(contentful): reenable support for gif images [PR #31986](https://github.com/gatsbyjs/gatsby/pull/31986)
+  - fix(gatsby-source-contentful): force base64 previews to be formatted as JPEG [PR #32155](https://github.com/gatsbyjs/gatsby/pull/32155)
+
+- [evank21](https://github.com/evank21): chore(docs): Fix typo in tutorial [PR #32050](https://github.com/gatsbyjs/gatsby/pull/32050)
+- [kdichev](https://github.com/kdichev): chore(gatsby-plugin-image): Add duotone, grayscale, rotate and trim options in transformOptions TS type [PR #31926](https://github.com/gatsbyjs/gatsby/pull/31926)
+- [stanulilic](https://github.com/stanulilic): docs: Fix typos in tutorial 4 [PR #31891](https://github.com/gatsbyjs/gatsby/pull/31891)
+- [alvis](https://github.com/alvis): fix(gatsby): correct args type in createParentChildLink [PR #32139](https://github.com/gatsbyjs/gatsby/pull/32139)
+- [justinyaodu](https://github.com/justinyaodu): chore(gatsby-plugin-mdx): Add comment why rehype-slug is required [PR #32128](https://github.com/gatsbyjs/gatsby/pull/32128)
+- [browniebroke](https://github.com/browniebroke): fix(gatsby): leave `xmlns` element when optimizing SVGs [PR #32123](https://github.com/gatsbyjs/gatsby/pull/32123)
+- [erezrokah](https://github.com/erezrokah): fix(plugin-netlify-cms): exclude cms.css from index.html [PR #32106](https://github.com/gatsbyjs/gatsby/pull/32106)
+- [herecydev](https://github.com/herecydev): feat(gatsby): Prevent generation of polyfill bundle if not needed [PR #31993](https://github.com/gatsbyjs/gatsby/pull/31993)
+- [alisson-suzigan](https://github.com/alisson-suzigan): chore(gatsby): Migrate schema-composer.js to TS [PR #31998](https://github.com/gatsbyjs/gatsby/pull/31998)
+- [gijsbotje](https://github.com/gijsbotje): chore(docs): Fix environment variables example [PR #32169](https://github.com/gatsbyjs/gatsby/pull/32169)
+- [AntoineGRoy](https://github.com/AntoineGRoy): chore(starters): Add a Gatsby CLI instructions link [PR #32158](https://github.com/gatsbyjs/gatsby/pull/32158)
+- [Pearce-Ropion](https://github.com/Pearce-Ropion): chore(netlify-cms): Bump webpack version to match gatsby [PR #32175](https://github.com/gatsbyjs/gatsby/pull/32175)
+- [jamesaucode](https://github.com/jamesaucode): chore(gatsby): Bumped express-graphql to v0.12.0 [PR #31178](https://github.com/gatsbyjs/gatsby/pull/31178)