Add types field to package.json

[andersk]

https://www.typescriptlang.org/docs/handbook/declaration-files/publishing.html#including-declarations-in-your-npm-package

Fixes this error:

$ npm i simplebar
$ tsc --init
$ echo 'import SimpleBar from "simplebar"' > test.ts
$ tsc
test.ts:1:23 - error TS7016: Could not find a declaration file for module 'simplebar'. '/tmp/test/node_modules/simplebar/dist/index.cjs' implicitly has an 'any' type.
  Try `npm i --save-dev @types/simplebar` if it exists or add a new declaration (.d.ts) file containing `declare module 'simplebar';`

1 import SimpleBar from "simplebar"
                        ~~~~~~~~~~~


Found 1 error in test.ts:1

[Grsmto]

Thanks @andersk 🙏

[Grsmto]

Published 6.2.3.