docs(maintainer): add maintainer governance docs

[d33bs]

Description

This PR adds documentation covering project roles and how to become a maintainer.

Closes #328

What is the nature of your change?

• Bug fix (fixes an issue).
• Enhancement (adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).
• This change requires a documentation update.

Checklist

Please ensure that all boxes are checked before indicating that a pull request is ready for review.

• I have read the CONTRIBUTING.md guidelines.
• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• New and existing unit tests pass locally with my changes.
• I have added tests that prove my fix is effective or that my feature works.
• I have deleted all non-relevant text in this pull request template.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.74%. Comparing base (b558b39) to head (7ce8e1c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #487   +/-   ##
=======================================
  Coverage   94.74%   94.74%           
=======================================
  Files          57       57           
  Lines        3156     3156           
=======================================
  Hits         2990     2990           
  Misses        166      166           

Flag	Coverage Δ
unittests	94.74% <ø> (ø)

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