chore(docs): bumped mkdocs-material to latest + small tweaks

[dreamorosi]

Description of your changes

This PR bumps the version of mkdocs-material to 9.0.2 (from 8.5.9) and introduces a handful minor tweaks to the docs:

• Consolidate primary & accent colors to deep orange in both light & dark themes
• Add option to dismiss announcements / banners
• Add icon links for repo & Discord Server in site footer

How to verify this change

See published version after merge.

Related issues, RFCs

Issue number: #1216

PR status

Is this ready for review?: YES
Is it a breaking change?: NO

Checklist

• My changes meet the tenets criteria
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in areas that should be flagged with a TODO, or hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding changes to the examples
• My changes generate no new warnings
• The code coverage hasn't decreased
• I have added tests that prove my change is effective and works
• New and existing unit tests pass locally and in Github Actions
• Any dependent changes have been merged and published
• The PR title follows the conventional commit semantics

Breaking change checklist

• I have documented the migration process
• I have added, implemented necessary warnings (if it can live side by side)

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