docs: improve mkdocs config

[AstreaTSS]

Pull Request Type

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

Description

This PR improves the mkdocs config by switching over to modern standards, largely:

• Adjusting the emoji index and generator to use the new, built-in paths instead of materialx. This gets rid of a lot of console spam noting how it's deprecated.
• Use groups instead of relying on contributors to manually comment out Insiders features so that contributing is much easier. This means any person can now clone the repo, use mkdocs serve after installing the dependencies, and it'll work without a complaint. The CI run should still function with Insider plugins working.

Changes

See description.

Related Issues

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