Aggregate account followers and channel followers in the UI

[LecygneNoir]

Hello,

Following side discussion on #2389 here is a suggestion about the counter that appears near the account name.

Currently, it shows the number of followers using mastodon to follow the account, as it's not possible at the moment to follow a regular account from Peertube.

Peertube user could only follow channel and not account, so it would be interesting if this counter aggregates both followers from mastodon and followers from channel.

Be careful that if a user (either from Mastodon or Peertube) follows multiple channels, it should be counted only one time?

However I think that beside this counter, keeping the counter for each channel is still interesting :-)

Thanks!

[rigelk]

@LecygneNoir I added a naive aggregation of followers count in a004ff1. I know it is not accurate since it doesn't check dinstinct actors that follow channels, but at least it is more reflective of an account's audience than the current account followers count (and faster to implement so it improves the situation for release 2.1 :)).