feat: add support for flat config

[G-Rath]

Checks

• I have read the contributing guidelines.

Changes

• Adds plugin name and version metadata (aka fix: add plugin name and version metadata for ESLint v9 #921)
• Adds flat versions of configs, for ESLint v9

Context

Resolves #902
Resolves #853

This uses a very similar approach to what I'm using for eslint-plugin-jest - the types should actually be pretty much correct, but I've just gone straight to casting since things are a bit of a mess right now ecosystem wise, which'll improve once we have everyone on ESLint v9.

Similarly I've not worried about adding any particular tests since the output is pretty stable and easily validated manually (which I have already), and I've based the documentation off what we use in eslint-plugin-jest too

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.32%. Comparing base (93a6ab9) to head (3dac688).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #923      +/-   ##
==========================================
+ Coverage   96.23%   96.32%   +0.08%     
==========================================
  Files          44       44              
  Lines        2419     2449      +30     
  Branches     1000     1018      +18     
==========================================
+ Hits         2328     2359      +31     
+ Misses         91       90       -1     

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[Belco90]

Thanks for adding flat config support in the current version ❤️

[github-actions]

🎉 This PR is included in version 6.3.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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