Show number of torrents using a tag in the `tag` administration tab

[josecelano]

The page to handle categories shows the number of torrents using a category:

But the page to edit tags does not show it:

I think it's a helpful feature to decide if you can remove an unused category without affecting any torrent.

You can get the number anyway by applying a filter on the URL:

• http://localhost:3001/torrents?categoryFilters=games
• http://localhost:3001/torrents?tagFilters=tag1

But I think the interface should be consistent and offer similar options if it's possible. I would keep the feature because the admin can get statistics, and there is no other way to get them now. You only can execute a database query.

[da2ce7]

• Associate Tags with Number of Usages torrust-index-gui#282