Empty page if no bridges available (zola)

On the [bridges page](https://matrix.turbo.fish/ecosystem/bridges/), you've got all the bridges, but heir are also some empty one. Like Mastodon and Tox. These link to an [empty page ](https://matrix.turbo.fish/ecosystem/bridges/mastodon/).

I understand the behavior (no bridges=empty page) but I feel like the page should at least mention that there aren't any bridges available.
Or there should be no link on the bridge overview if there are no bridges.
Or we just need a Mastodon and Tox bridge 😄

Start with the bridges overview and the empty Mastodon and Tox pages linked in the issue. Clarify whether empty entries should show an explanatory message or have no link, then verify that the chosen behavior applies when no bridges are available and that the pages no longer appear empty or misleading.

Written by the indexing model from the issue text.