DOC: Release guidelines.

RELEASE_GUIDELINES.md

+# Release Guidelines for the CaosDB Python Client Library
+
+This document specifies release guidelines in addition to the general release
+guidelines of the CaosDB Project
+([RELEASE_GUIDELINES.md](https://gitlab.com/caosdb/caosdb/blob/dev/RELEASE_GUIDELINES.md))
+
+## General Prerequisites
+
+* All tests are passing.
+* FEATURES.md is up-to-date and a public API is being declared in that document.
+* CHANGELOG.md is up-to-date.
+* DEPENDENCIES.md is up-to-date.
+
+## Steps
+
+1. Create a release branch from the dev branch. This prevents further changes
+   to the code base and a never ending release process. Naming: `release-<VERSION>`
+
+2. Update CHANGELOG.md
+
+3. Check all general prerequisites.
+
+4. Update the version:
+   - `version` variables in `docs/conf.py`
+   - Version on [setup.py](./setup.py): Check the `MAJOR`, `MINOR`, `MICRO`, `PRE` variables and set
+     `ISRELEASED` to `True`. Use the possibility to issue pre-release versions for testing.
+
+5. Merge the release branch into the main branch.
+
+6. Tag the latest commit of the main branch with `v<VERSION>`.
+
+7. Delete the release branch.
+
+8. Remove possibly existing `./dist` directory with old release.
+
+9. Publish the release by executing `./release.sh` with uploads the caosdb
+   module to the Python Package Index [pypi.org](https://pypi.org).
+
+10. Merge the main branch back into the dev branch.
+
+11. After the merge of main to dev, start a new development version by
+    setting `ISRELEASED` to `False` and by increasing at least the `MICRO`
+    version in [setup.py](./setup.py) and preparing CHANGELOG.md.