Social networks field on user profiles

[JohnXLivingston]

Describe the problem to be solved

As said in #5429 , Mastodon can mark a link in user profiles as verified if the distant page point to the user profile with a "a" tag having a rel="me" attribute.
This is very usefull to authenticate users on the fedivers.

Peertube users should be able to add one or many links to their websites and social networks.
These links would be shown on the user's page, and could be used to verify links on Mastodon-like profiles.
They would also be added to the AP user informations.

Peertube could also implement the same verifying procedure (check that the remote page has a link to the user profile, with rel="me").

Describe the solution you would like

In your account options, their would be a given number of fields to add external links.
Such field could be doubled with a description field where the user could add a label to the link.

On the user's profile, these links would be shown, with a rel="me" attribute.

Note: Mastodon does not render the Javascript when verifying remote links. So Peertube should also add these links in the backend generated DOM when accessing a user's page.

[FediVideos]

Just had user request this via FediTips, they have linked to their PeerTube account and would like it to turn green on their Mastodon account. Would be great if there was some kind of dedicated part of the PeerTube profile that includes rel=me