doc: add litgen to the automatic generators list (compiling.rst) (#5012)

* doc: add litgen to the automatic generators list (compiling.rst)

Added this:

[litgen]_ is an automatic python bindings generator with a focus on generating
documented and discoverable bindings: bindings will nicely reproduce the documentation
found in headers. It is is based on srcML (srcml.org), a highly scalable, multi-language
parsing tool with a developer centric approach. The API that you want to expose to python
must be C++14 compatible (but your implementation can use more modern constructs).

.. [litgen] https://pthom.github.io/litgen

* style: pre-commit fixes

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

docs/compiling.rst

@@ -639,3 +639,11 @@ cross-project dependency management. Additionally, it is able to autogenerate
 customizable pybind11-based wrappers by parsing C++ header files.
 
 .. [robotpy-build] https://robotpy-build.readthedocs.io
+
+[litgen]_ is an automatic python bindings generator with a focus on generating
+documented and discoverable bindings: bindings will nicely reproduce the documentation
+found in headers. It is is based on srcML (srcml.org), a highly scalable, multi-language
+parsing tool with a developer centric approach. The API that you want to expose to python
+must be C++14 compatible (but your implementation can use more modern constructs).
+
+.. [litgen] https://pthom.github.io/litgen