Add Continuous Integration

[AntoinePrv]

Github Action seems to be the best option to get CI on MacOS, Windows, and Linux.

We don't have Bliss tests for now so maybe we can start with:

• testing the Bliss compiles
• Testing the CMake installs
• A short program to test that bliss can be found and linked against

What do we want to support:

• Gcc >= ???, Clang >= ???, AppleClang >= ???, MSVC >= ???
• Windows, MacOs, Linux. Is 64 bits enough ?
• CMake >= ???

cc: @fschloesser @matbesancon

[fschloesser]

I would start supporting gcc and clang, 64 bits for the three main platforms and cmake 3.10 upwards (that is the standard for ubuntu 3.10, which we are using atm)