[Task] Add Contributing md (#1769)

* Add CONTRIBUTING.md

* Change

Author: martineiber

CONTRIBUTING.md

@@ -0,0 +1,10 @@
+## Contributing Studio Pull Requests
+We gladly accept community pull requests. This is the preferred way to contribute to Pimcore. There are a few necessary steps before we can accept a pull request:
+
+* [Fork us!](https://help.github.com/articles/fork-a-repo/)
+* Select the right branch. `main`(`2026.x`) for features and improvements or latest maintenance branch for bug fixes (`2025.4`)
+* [Send a pull request](https://help.github.com/articles/using-pull-requests/) from your fork’s branch to our repo branch.
+* [Sign the CLA](https://cla-assistant.io/pimcore/pimcore) - see also below.
+* Ensure that Github pipelines pass (linter, tests...)
+
+For details please check also the contributing docs of [pimcore/pimcore](https://github.com/pimcore/pimcore/blob/2026.x/CONTRIBUTING.md).

README.md

@@ -39,3 +39,11 @@ This bundle requires the following dependencies:
 - [Installation and Configuration](./doc/02_Installation_and_Configuration/README.md)
 - [Extending](./doc/03_Extending/README.md)
 - [Development Details](./doc/04_Development_Details/README.md)
+
+
+## Contribute
+**Bug fixes:** please create a pull request including a step by step description to reproduce the problem  
+**Contribute features:** contact the core-team via issue before you start developing   
+**Security vulnerabilities:** please see our [security policy](https://github.com/pimcore/pimcore/security/policy)
+
+For details, please have a look at our [contributing guide](CONTRIBUTING.md).