Add venv-build-env.sh

```shell-session
$ source ./venv-build-env.sh
$ cd projects/librobotcontrol/docs
$ doxygen
$ cd ../../..
$ sphinx-build -M html . public
```

venv-build-env.sh

+#!/bin/sh
+# Source this script
+if [ ! -e ./sphinx-env ]; then
+   python3 -m venv sphinx-env
+fi
+source ./sphinx-env/bin/activate
+python3 -m pip install --upgrade pip
+python3 -m pip install sphinx==5.3.0 sphinx-rtd-theme sphinx_design sphinx-tabs sphinxcontrib.svg2pdfconverter sphinx-reredirects
+python3 -m pip install sphinxcontrib-images
+python3 -m pip install breathe exhale