Add contribution guidelines

CONTRIBUTING.md

@@ -0,0 +1,53 @@
+# Contributing to the BCI-dockerfile-generator
+
+##  Opening an Pull Request
+
+The BCI-dockerfile-generator documentation has a section on contributing a
+new container or modifying an existing container. Please check the chapter
+**Adding and modifying containers** for details.
+
+Before creating a pull request, please format your source code with Ruff,
+which is installed in the Poetry virtual environment by default:
+
+```bash
+poetry run ruff format
+# reorder imports:
+poetry run ruff check --fix
+```
+
+Additionally, run the unit tests and check whether the documentation builds
+(additional points if you update it):
+
+```bash
+# tests
+poetry run pytest -vv
+# docs
+poetry run sphinx-build -M html source build -W
+```
+
+
+## Reviewing a Pull Request
+
+The following guidelines are respected by the maintainers on reviewing a Pull Request:
+
+* CI failures are treated seriously. As a general rule changes with failing CI are not being merged.
+
+* A reviewer who has requested a change should be notified when the feedback
+has been handled. This can be done by clicking the "re-request review" button
+on the particular reviewers handle.
+
+* A pull request is considered mergeable if it has no outstanding change
+requests, at least one approval by the maintainers and sufficient time has
+passed. Sufficient time means a business workday since initial creation.
+
+* For changes that touch areas where there are subject matter experts (e.g.
+the documentation team for documentation changes), the reviewer or the author
+of the PR takes responsibility that these experts had an opportunity to
+provide feedback before merging.
+
+* *Single Review*: The reviewers address the most important issues in the
+first review. Minor issues can be commented, for example with a 'NIT:'
+prefix. These can be addressed in a followup change or documented for later
+in an issue tracker entry. We avoid trickling in further feedback over the
+whole review process so that the pull request author understands what the
+outstanding action items are upfront.

README.rst

@@ -65,6 +65,10 @@ Additionally, run the unit tests and check whether the documentation builds
    poetry run sphinx-build -M html source build -W
 
 
+Further Contributing Guidelines are defined in the `CONTRIBUTING.md` file
+in the root directory of the project.
+
+
 Documentation - READMEs
 ^^^^^^^^^^^^^^^^^^^^^^^