Update contribution guide.

CONTRIBUTING.md

@@ -36,10 +36,9 @@ a few of which we want to mention here:
 * Ask clarifying questions on recently opened issues to move the discussion forward
 
 ### You like coding?
-* Find open issues and resolve them
-* Implement new features
+* Find [open issues](https://github.com/gurkenlabs/litiengine/issues) and resolve them
+* Implement [new features](https://github.com/gurkenlabs/litiengine/issues?q=is%3Aopen+is%3Aissue+label%3Afeature)
 * Automate project setup
-* Help us develop an eclipse plugin for project setup
 * Improve tooling and testing
 * Enhance LITIENGINE workflows by improving the utiLITI editor.
 
@@ -54,7 +53,18 @@ a few of which we want to mention here:
 Well... if you still want to support us, you could consider helping us bear the development costs for LITIENGINE (e.g. servers and equipment).
 You can do so by sponsoring [LITIENGINE on OpenCollective](https://opencollective.com/litiengine) or sponsoring the devs [Steffen](https://github.com/sponsors/steffen-wilke) and [Matthias](https://github.com/sponsors/nightm4re94) directly on GitHub.
 
-## How do I contribute to the LITIENGINE repository?
+## Code contributions
+### Setting up your development environment
+* [Install JDK 17](https://litiengine.com/docs/getting-started/install-jdk/)
+* [Clone the LITIENGINE repository](https://github.com/gurkenlabs/litiengine.git)
+* Open the LITIENGINE project in [your IDE of choice](https://litiengine.com/docs/getting-started/development-environment/)
+* Make sure that the project is imported as a Gradle project
+* Make sure that the project is compiled with JDK 17 and that JDK 17 is also set as your Gradle runtime
+* Use Gradle to build the project. You can do this via the UI, or open a terminal in the project's root folder and type `./gradlew build`.
+* If the build was successful, you have now completed all steps required for contributing to LITIENGINE development. Continue with the next section.
+* Having any trouble? Ask for help in the [GitHub discussions](https://github.com/gurkenlabs/litiengine/discussions) or on our [Discord server](https://discord.com/invite/rRB9cKD).
+
+### Submitting code contributions
 * Create a GitHub account
 * Fork the [LITIENGINE repository](https://github.com/gurkenlabs/litiengine)
 * Create a thematically labelled branch
@@ -66,9 +76,8 @@ You can do so by sponsoring [LITIENGINE on OpenCollective](https://opencollectiv
 * File a Pull Request
  * We try to review pull requests as often as possible, but don't be mad if it takes us some days before reviewing yours.
  * As soon as your changes were reviewed and approved, we will merge them into the master branch.
- * Due to questionable design decisions, violations of our code of conduct, or bugs, we may reject pull requests. Again, this is nothing to be mad about: After you've revised the defective portions of your pull request, we'll happily review it once more.
+ * Due to questionable design decisions, violations of our code of conduct, or bugs, we may reject pull requests and ask for changes. Again, this is nothing to be mad about: After you've revised the defective portions of your pull request, we'll happily review it once more.
  * Changes resulting in build and test pipeline failures that cannot be resolved within two days will be reverted.
-
 
 ### Style Guide
 Code in the LITIENGINE repository needs to be formatted in compliance with the **gurkenlabs Java code style**. You can use the configuration file provided in [`config/gurkenlabs.eclipseformat.xml`](config/gurkenlabs.eclipseformat.xml).