[Docs] Use emoji for jsx-runtime config and config file for eslint-doc-generator

[bmish]

1. Switch to using .eslint-doc-generatorrc.js config file. Optional but nice.
2. Use 🏃 emoji to represent jsx-runtime instead of a badge (follow-up to Update eslint-doc-generator to v1.0.0 #3499 (comment)). The emoji is more consistent with how we represent other configs, more portable (shows up in all docs, not just the README), and just more aesthetic. The badge was also showing up too small and difficult to read for some reason.

[codecov]

Codecov Report

Merging #3504 (c9f5eb2) into master (a60f04d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3504   +/-   ##
=======================================
  Coverage   97.57%   97.57%           
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  Files         130      130           
  Lines        9211     9211           
  Branches     3341     3341           
=======================================
  Hits         8988     8988           
  Misses        223      223           

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[ljharb]

is there a reason this has to be a JS file? ideally config is static.

(it's also a bit confusing to have "rc" in the name when it's not actually an rc file, but i guess eslintrc already makes that mistake)

[bmish]

Any filename or format from here is supported: https://github.com/davidtheclark/cosmiconfig#searchplaces (more info: https://github.com/bmish/eslint-doc-generator#configuration-file).

Note that only a JavaScript format enables us to benefit from the type definitions (auto-complete, hover-over documentation, etc).

[ljharb]

Since presumably the tool validates the config at runtime, I'm not super worried about the type definitions, but fair point.

[bmish]

Yeah the types are just a convenience. The config file is fully validated at runtime.