Backport #28160 by @yp05327
Since #27054, Actions are enabled by default. so we should also edit the
document. 😃
ps: I think this should be backport to 1.21.0.
Co-authored-by: yp05327 <576951401@qq.com>
This PR cleans up the docs in a way to make them simpler to ingest by
our [docs repo](https://gitea.com/gitea/gitea-docusaurus).
1. It includes all of the sed invocations our ingestion did, removing
the need to do it at build time.
2. It replaces the shortcode variable replacement method with
`@variable@` style, simply for easier sed invocations when required.
3. It removes unused files and moves the docs up a level as cleanup.
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Signed-off-by: jolheiser <john.olheiser@gmail.com>
