Add initial rule docs

Initial support for generating them and keeping them in sync. A lot of links need to be fixed since the docs currently assume they are part of the build encyclopedia. Will fix all that in a follow up.

Copybara Import from https://github.com/bazelbuild/rules_java/pull/224

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Add initial rule docs (#224)

Closes #224
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COPYBARA_INTEGRATE_REVIEW=https://github.com/bazelbuild/rules_java/pull/224 from bazelbuild:hvd_docs 0782c46b60b17a0604770a43f3ff9035c32088e6
PiperOrigin-RevId: 677744490
Change-Id: I4bf451cd05fe1838dcec3b3987c62fb134bc0e3f