docs: add contributing file (#238)

Author: chr-hertel

CONTRIBUTING.md

@@ -0,0 +1,41 @@
+# Contributing
+
+You want to contribute to this project? Great! We are happy to welcome you to the repository. Please read the following
+guidelines to get started. It will help to make the contribution process easy and effective for everyone involved.
+
+## Disclaimer
+
+Before you start contributing, please be aware that this project is not commercial and is maintained by volunteers in
+their free time to share code among themselves and with the community. We are happy to invest our time in this project
+and to share it with you. However, we cannot guarantee that we will be able to respond to your requests in a timely
+manner or that we will be able to implement your suggestions.
+
+## Questions and Support
+
+If you have any questions or problems while using LLM Chain, please check the [README](README.md) file and also the
+[examples](examples) folder. If you can't find the answer there, feel free to open an
+[issue](https://github.com/php-llm/llm-chain/issues).
+
+## Bug Reports 
+
+If you open an issue to report a bug, please make sure to provide enough information to reproduce the bug. Ideally even
+provide a code snippet that reproduces the bug. This will help us to fix the bug faster.
+
+## Feature Ideas
+
+Of course, we are happy to get your ideas for new features. And for sure, we are happy if you want to implement them.
+However, to make sure that you are not wasting your time, please open an issue first to discuss your idea in case it is
+a larger change.
+
+## Pull Requests
+
+When you end up implementing a new feature or fixing a bug, please open a pull request. The pipeline will help you to
+check if your code is following the coding standards and if all tests are passing. To execute the tools locally, you
+can use the following commands:
+
+```bash
+make qa
+make qa-lowest
+``` 
+
+Commit messages should follow the [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/) specification.

README.md

@@ -671,7 +671,8 @@ final class MyProcessor implements OutputProcessor, ChainAwareProcessor
 
 ## Contributions
 
-Contributions are always welcome, so feel free to join the development of this library.
+Contributions are always welcome, so feel free to join the development of this library. To get started, please read the
+[contribution guidelines](CONTRIBUTING.md).
 
 ### Current Contributors