Fix Vector2 for GCC11

Improve the priority queue implementation

Improve the README

Fix a typo in the gitignore file that prevents from staging mainpage.h

Revert commit f48f74

Update the Doxyfile

Add more comments to the code

Make constructors with only one argument explicits

Improve error handling

Replace #include <iostream> by #include <iosfwd>

Make the simple functions from util constexpr and noexcept

Improve the interface of Diagram

Complete CMakeLists.txt to make the library installable

Fix some styling issues

Add badges in the README