Open Source PyMOL 2.6.0a0 for Python 3.12

Major changes:

• Update wheels from Python v3.11 to Python v3.12 (bee4724);
• Update Bug Report Issue template (bee4724);
• Update Testing Workflow (ec9e48f, bee4724);
• Update documentation (bee4724, 7453413, 1948b51, bcfe4c2);

Full Changelog: v2.6.0a0-cp311...v2.6.0a0-cp312