Version 0.4.0

This release primarily drops Python 3.6 support. It also adds official 3.12 support. The changelog is now part of the docs.

• chore: drop Python 3.6 by @henryiii in #84
• chore: move to using Ruff by @henryiii in #86
• ci: fix readthedocs by @henryiii in #99
• chore: target-version no longer needed by Black or Ruff by @henryiii in #103
• chore: sp-repo-review by @henryiii in #107
• docs: prepare for schema addition by @henryiii in #113
• chore: add a check and bump NumPy by @henryiii in #114
• docs: add changelog by @henryiii in #115

Full Changelog: v0.3.3...v0.4.0