Severin Strobl

Upgrade third-party dependency Eigen to version 3.4

1

Recently Eigen 3.4.0 was [released](https://eigen.tuxfamily.org/index.php?title=3.4), marking the first major release in a while. The overlap library should be tested with this release and if everything works out the Eigen sub-module...

Build Python wheels for AArch64

1

Using `cibuildwheel` it should be [fairly easy](https://cibuildwheel.readthedocs.io/en/stable/faq/#emulation) to also build the Python wheels for non-native architectures, in particular AArch64.

Expose include directory as system path via CMake

1

## Description Treading the include directory as a system include directory prevents clang-tidy from emitting errors from the doctest headers, avoiding issues when using various doctest macros.