docs: added contribution guide draft

Author: jankapunkt

CONTRIBUTING.md

@@ -0,0 +1,119 @@
+# Contributing to @node-oauth/oauth2-server
+
+Thank you for your interest in this project and your aims to improving it.
+This guide will give you the most important info on how to contribute properly
+in order to get your pull requests accepted.
+
+## Disclose security vulnerabilities
+
+First things first:
+This project has strong security implications and we appreciate every help to
+improve security.
+
+**However, please read our [security policy](./SECURITY.md), before taking 
+actions.**
+
+## Development
+
+If you want to fix bugs or add new features, please clone the source via
+
+```bash
+$ npm run test
+```
+
+### No PR without issue
+
+Please make sure your commitment will be appreciated by first opening an issue
+and discuss, whether this is a useful addition to the project.
+
+
+### Run the tests
+
+Please always make sure your code is passing linter and tests **before** 
+committing. By doing so you help to make reviews much easier and don't pollute 
+the history with commits, that are solely targeting lint fixes.
+
+You can run the tests via
+
+```bash
+$ npm run test
+```
+
+or  
+
+```bash
+$ npm run test:coverage
+```
+
+to see your coverage.
+
+### Open a pull request (PR) 
+
+Once you have implemented your changes and tested them locally, please open
+a [pull request](https://docs.github.com/en/github/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request).
+
+Note: sometimes a pull request (PR) is also referred to as merge request (MR).
+
+#### Fundamental PR requirements
+
+There are a few basic requirements for your pull request to become accepted:
+
+- Make sure to open your pull request to target the `development` branch and not 
+`master`
+- Make sure you are working on a branch, other than `development`; usually you
+  can name the branch after the feature or fix you want to provide
+- Resolve any merge conflicts (usually by keeping your branch updated with 
+  `development`)
+- Have a clear description on what the PR does, including any steps necessary
+  for testing, reviewing, reproduction etc.
+- Link to the existing issue
+- Added functions or changed functions need to get documented in compliance with
+  JSDoc
+- Make sure all CI Tests are passing
+
+Also make sure, to comply with the following list:
+
+- Do not work on `development` directly
+- Do not implement multiple features in one pull request (this includes bumping
+  versions of dependencies that are not related to the PR/issue)
+- Do not bump the release version (unless you are a maintainer)
+- Do not edit the Changelog as this will be done after your PR is merged
+- Do not introduce tight dependencies to a certain package that has not been
+  approved during the discussion in the issue
+
+#### Review process
+
+Finally your PR needs to pass the review process:
+
+- A certain amount of maintainers needs to review and accept your PR
+- Please **expect change requests**! They will occur and are intended to improve
+  the overall code quality.
+- If your changes have been updated please re-assign the reviewer who asked for
+  the changes
+- Once all reviewers have approved your PR it will be merged by one of the
+  maintainers :tada:
+
+## For maintainers
+
+### When to release a new version?
+
+- on fixed vulnerabilities
+- on fixed dependency-vulnerabilites
+- on new added features
+- what else?
+
+### When to decide between major, minor and path release?
+
+- major = breaking
+- minor = features and security fixes
+- patch = general fixes and small improvements
+
+### How to release a new version?
+
+What's required to publish to npm, which branches are involved, what should not
+be done etc.
+
+## Become a maintainer
+
+What is required to become a maintainer?
+ 

README.md

@@ -40,12 +40,8 @@ This module has been rewritten using a promise-based approach, introducing chang
 
 Please refer to our [3.0 migration guide](https://oauth2-server.readthedocs.io/en/latest/misc/migrating-v2-to-v3.html) for more information.
 
+## Contributing to this project
 
-## Tests
-
-To run the test suite, install dependencies, then run `npm test`:
-
-```bash
-npm install
-npm test
-```
+Please read our [contribution guide](./CONTRIBUTING.md) before taking actions.
+In any case, please open an issue before opening a pull request to find out,
+whether your intend to contribute will actually have a chance to be merged.