🩹 make sure to activate the venv in RtD build (#717)

## Description

This PR makes sure that the virtual environment in the RtD build is
activated so that the installed console-scripts become available.

## Checklist:

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- [x] The pull request only contains commits that are related to it.
- [x] I have added appropriate tests and documentation.
- [x] I have made sure that all CI jobs on GitHub pass.
- [x] The pull request introduces no new warnings and follows the
project's style guidelines.

Author: burgholzer

.readthedocs.yaml

@@ -25,13 +25,13 @@ build:
     # Install the project and its documentation dependencies
     - uv pip install .[docs] readthedocs-sphinx-ext
     # Run the html builder
-    - .venv/bin/python -m sphinx -T -b html -d docs/_build/doctrees -D language=en docs $READTHEDOCS_OUTPUT/html
+    - . .venv/bin/activate && .venv/bin/python -m sphinx -T -b html -d docs/_build/doctrees -D language=en docs $READTHEDOCS_OUTPUT/html
     # Run the htmlzip builder and create a zip file
-    - .venv/bin/python -m sphinx -T -b dirhtml -d docs/_build/doctrees -D language=en docs docs/_build/dirhtml
+    - . .venv/bin/activate && .venv/bin/python -m sphinx -T -b dirhtml -d docs/_build/doctrees -D language=en docs docs/_build/dirhtml
     - mkdir -p $READTHEDOCS_OUTPUT/htmlzip
     - zip -r $READTHEDOCS_OUTPUT/htmlzip/html.zip docs/_build/dirhtml/*
     # Run the latex builder and create a pdf file
-    - .venv/bin/python -m sphinx -T -b latex -d docs/_build/doctrees -D language=en docs docs/_build/latex
+    - . .venv/bin/activate && .venv/bin/python -m sphinx -T -b latex -d docs/_build/doctrees -D language=en docs docs/_build/latex
     - cd docs/_build/latex && latexmk -pdf -f -dvi- -ps- -interaction=nonstopmode -jobname=$READTHEDOCS_PROJECT
     - mkdir -p $READTHEDOCS_OUTPUT/pdf
     - cp docs/_build/latex/$READTHEDOCS_PROJECT.pdf $READTHEDOCS_OUTPUT/pdf/$READTHEDOCS_PROJECT.pdf