feat: update docs and support state for custom statuses

[AstreaTSS]

Pull Request Type

• Feature addition
• Bugfix
• Documentation update
• Code refactor
• Tests improvement
• CI/CD pipeline enhancement
• Other: [Replace with a description]

Description

Setting state for presences for bots is now supported, as seen by this changelog, allowing for custom statuses (among other things). Technically, existing interactions.py versions can already use this through a raw dictionary and using the gateway's change_presence, but this PR makes it possible to use more normal means, and also updates the docs to note about it.

Changes

• Update the docs about Activity.state.
• Allow setting state through Activity.create.
• Pass in state in the to_dict method.

Related Issues

#1526

Test Scenarios

Python Compatibility

• I've ensured my code works on Python 3.10.x
• I've ensured my code works on Python 3.11.x

Checklist

• I've run the pre-commit code linter over all edited files
• I've tested my changes on supported Python versions
• I've added tests for my code, if applicable
• I've updated / added documentation, where applicable