Release 0.6.0

Release 0.6.0 brings the following changes:

• Full compatibility across OSes (thanks to cpymad's progress)

• Added a tfstools module

• Added a beam module in optics

• Added an (experimental) timedata module in plotting

• Improved object validation with pydantic

• Made cpymad a default dependency

• Added a docs dependency

• Updated dependencies.

• Moved CI to Github Actions, now covers all platforms

• Improved test coverage.

• Started documentation site