Release v0.2-aplha.3

Many new functionalities, which are not documented correctly yet.

• The Protein objects now consist of AminoAcid objects.
• The AminoAcid objects form the internal linkage, while the Protein objects manage the total space for folding.
• The internal workings of Protein have been fully re-designed and function calls are now easier.
• A Pytest test suite has been made for the workings of Protein and the algorithms.
• There is a core test suite written in C++ to test the core without building the Python module.
• Upped the minimum required Python version to 3.9.
• GitHub actions versions have been increased, and we now build for specific Python versions.
• Documentation was added, but requires updating.
• Prospr now has its own logo!