docs(project): improve contributing guides

* update CONTRIBUTING.md
* add ISSUE_TEMPLATE.md
* add PULL_REQUEST_TEMPLATE.md

Related to bpmn-io/bpmn-js#714

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,16 @@
+<!--
+
+Make sure to checkout [CONTRIBUTING.md](https://github.com/bpmn-io/diagram-js/blob/master/CONTRIBUTING.md#creating-an-issue) before filing a bug or feature request.
+
+If possible, reproduce bugs through a [test case](https://github.com/bpmn-io/diagram-js/tree/master/test/spec).
+
+-->
+
+
+### Expected Behavior
+
+
+### Actual Behavior
+
+
+### Steps to reproduce the Behavior

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,17 @@
+<!--
+
+Thanks for filing a pull request!
+
+Make sure you've read through [our contributing guide](https://github.com/bpmn-io/diagram-js/blob/master/CONTRIBUTING.md#creating-a-pull-request) before you continue.
+
+-->
+
+
+Fixes #
+
+
+### Proposed Changes
+
+*
+*
+*

CONTRIBUTING.md

@@ -1,37 +1,89 @@
-# How to contribute
+# How to Contribute
 
-We love you to contribute to this project by filing bugs, helping others on the [issue tracker](https://github.com/bpmn-io/diagram-js/issues), by contributing features/bug fixes through pull requests or by helping out in our [forums](https://forum.bpmn.io/).
+Great to see you! Help us out by [filing bugs or feature requests](#working-with-issues), assisting others in our [forums](https://forum.bpmn.io/) or by [contributing improvements](#contributing-improvements).
 
-## How to start with diagram-js
 
-
-    mkdir bpmn.io
-    cd bpmn.io
+## Table of Contents
 
-    git clone [email protected]:bpmn-io/diagram-js.git
-    (cd diagram-js && npm i)
+* [Working with Issues](#working-with-issues)
+    * [Creating an Issue](#creating-an-issue)
+    * [Helping out](#helping-out)
+* [Contributing Improvements](#contributing-improvements)
+    * [Setting up the Project locally](#setting-up-the-project-locally)
+    * [Discussing Code Changes](#discussing-code-changes)
+    * [Creating a Pull Request](#creating-a-pull-request)
 
-    // Run the test suite
-    grunt
-
-    // Running the test suite with every file change
-    TEST_BROWSERS=(Chrome|Firefox|IE) grunt auto-test
 
-## Working with issues
+## Working with Issues
 
-We use our [issue tracker](https://github.com/bpmn-io/diagram-js/issues) for project communication.
-When using the issue tracker,
+We use our [issue tracker](https://github.com/bpmn-io/diagram-js/issues) for project communication, discussion and planning.
 
-* Be descriptive when creating an issue (what, where, when and how does a problem pop up)?
-* Attach steps to reproduce (if applicable)
-* Attach code samples, configuration options or stack traces that may indicate a problem
+
+### Creating an Issue
+
+Help others to understand your request:
+
+* Be clear whether you [file a bug](#reporting-a-bug) or [suggest a new feature/improvement](#suggesting-a-feature)
+* Be descriptive when reporting (what, where, when and how)
+
+
+#### Reporting a Bug
+
+Help us to understand and reproduce your issue:
+
+* Attach your environment (browser, diagram-js version)
+* Attach steps to reproduce
+* Attach code samples, configuration options or stack traces that provide the necessary context
+
+If possible, try to build [a test case](https://github.com/bpmn-io/diagram-js/tree/master/test/spec) that reproduces your problem.
+[See below](#setting-up-the-project) how to setup diagram-js for development.
+
+
+#### Suggesting a Feature
+
+* Provide the necessary context that allows us to understand how your proposal improves our library
+
+
+### Helping out
+
+* Share your perspective on issues
 * Be helpful and respect others when commenting
 
-Create a pull request if you would like to have an in-depth discussion about some piece of code.
 
-## Creating pull requests
+## Contributing Improvements
+
+Learn how to setup the project locally, make changes and contribute bug fixes and new features through pull requests.
 
-We use pull requests for feature discussion and bug fixes. If you are not yet familiar on how to create a pull request, [read this great guide](https://gun.io/blog/how-to-github-fork-branch-and-pull-request).
+### Setting up the Project
+
+If you don't have [NodeJS](https://nodejs.org/en/download/) setup, do it beforehand.
+
+The following code snippet sets up diagram-js on your machine.
+
+```plain
+mkdir bpmn.io
+cd bpmn.io
+
+git clone [email protected]:bpmn-io/diagram-js.git
+(cd diagram-js && npm install)
+
+// Run the test suite
+bon test
+
+// Running the test suite with every file change
+TEST_BROWSERS=(Chrome|Firefox|IE) npm run dev
+```
+
+
+
+### Discussing Code Changes
+
+Create a [pull request](#creating-a-pull-request) if you would like to have an in-depth discussion about some piece of code.
+
+
+### Creating a Pull Request
+
+We use pull requests for feature additions and bug fixes. If you are not yet familiar on how to create a pull request, [read this great guide](https://gun.io/blog/how-to-github-fork-branch-and-pull-request).
 
 Some things that make it easier for us to accept your pull requests
 
@@ -40,9 +92,12 @@ Some things that make it easier for us to accept your pull requests
     * single-quotes
     * ...
 * The code is tested
-* The `grunt` build passes (executes tests + linting)
+* The `npm run all` build passes (executes tests + linting)
 * The work is combined into a single commit
 * The commit messages adhere to our [guideline](https://docs.google.com/document/d/1QrDFcIiPjSLDn3EL15IJygNPiHORgU1_OOAqWjiDU5Y)
 
 
-We'd be glad to assist you if you do not get these things right in the first place.
+We'd be glad to assist you if you do not get these things right in the first place.
+
+
+:heart: from the bpmn.io team.