Add tool links to Pull Requests

[ericcornelissen]

It would be useful if the Pull Requests created by the tool-versions-update-action/pr Action include a link to the tool just like Dependabot does. I find myself wanting to go check the change log or release notes of the tool being updated to find out what changed, and a link to the project would make this a bit easier. asdf has the (admittedly optional) bin/help.links script that plugins can implement to give the user links for the tool, this could probably be used for this purpose.

[ericcornelissen]

It seems there is no way to get asdf to just output the links, only asdf help <plugin> which outputs all bin/help.* scripts. Instead, it would be possible to invoke ~/.asdf/plugins/<plugin>/bin/help.links directly.