added angular (dihedral and angle) constraints and proper printing for XTB (only)

[rmacknight99]

Checklist

• [ ] The changes include an associated explanation of how/why
• [ ] Test pass
• [ ] Documentation has been updated
• [ ] Changelog has been updated

[rmacknight99]

added angular (dihedral and angle) constraints to constraints.py and proper printing for XTB (only)

[t-young31]

Hi @rmacknight99 – thanks for the PR, looks great! Would you mind adding the following?

• (most important!) add yourself to the contributors list
• Extracting the common functionality between the distance and angle constraints class to reduce the duplication
• Raise a NotImplemeted error in the wrappers that don't implement the angular constraint functionality
• Create tests in tests/test_wrappers/test_xtb.py that assert the expected output (example), rather than tests/test_angular_constraints.py

Thanks 😄

[t-young31]

This has been hanging for >1 month, so I'm going to close it. Feel free to reopen if you get a chance to work on it!