Merge commit '70a58c5' into feature-bump-merge-3

We add `./tmp` to ensure we can make a commit to connect history with
upstream in a fast-forward way

# Conflicts:
#	.github/workflows/ci.yml
#	.github/workflows/format.yml
#	.github/workflows/pip.yml
#	README.rst
#	docs/advanced/cast/overview.rst
#	include/pybind11/cast.h
#	include/pybind11/detail/internals.h
#	include/pybind11/detail/type_caster_base.h
#	include/pybind11/eigen.h
#	include/pybind11/pybind11.h
#	tests/test_eigen.cpp
#	tests/test_multiple_inheritance.cpp