Backport #28639 by @denyskon
According to [Debian
docs](https://wiki.debian.org/DebianRepository/UseThirdParty):
> The certificate MUST NOT be placed in /etc/apt/trusted.gpg.d or loaded
by apt-key add.
> ...
> If future updates to the certificate will be managed by an apt/dpkg
package as recommended below, then it SHOULD be downloaded into
/usr/share/keyrings using the same filename that will be provided by the
package. If it will be managed locally , it SHOULD be downloaded into
/etc/apt/keyrings instead.
> ...
> A sources.list entry SHOULD have the signed-by option set.
Co-authored-by: Denys Konovalov <kontakt@denyskon.de>
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.
---------
Signed-off-by: jolheiser <john.olheiser@gmail.com>
