Adds a confirmation similar to the one performed during plugin
installation, when adding a 3rd party repository.
The safe domain is hardcoded to be "repo.jellyfin.org" as this is very
stable and we have no plans to change it. Individual mirrors don't need
to be specified since this is user-input content and they should be
using the main URL not the URL of a specific mirror.
The confirmation message makes explicit mention of the possibility of
malicious code from 3rd party repositories as well as updates that may
bring it in, and suggests only adding 3rd parties from trusted people.
The plugin install confirmation is also modified to use the same
conditional and an altered message similar to the above, again to
emphasize the potential security risks of 3rd party plugins.
Finally, some additional information is added to the Developer Info
section of the plugin page; specifically, the name of the repository the
plugin is sourced from as well as its URL. How this is obtained is a
hack, since these should probably be part of the main information about
the plugin and not each specific version, but this is worked around by
only showing the information from the first (i.e. newest) version.
