Option to add Fediverse instances (Mastodon & Bluesky)

[WalsGit]

Feature Request

Is your feature request related to a problem? Please describe.

The S9e Text Formatter currently only supports mastodon.social toot embeds but as you know there are thousands of instances.

Describe the solution you'd like
Although I know it isn't the best idea to add them all (and there's an api to get them) but the better solution, i think, is to offer an option in the admin panel for manually add as many instances as the admin needs for his Flarum community, via a text field with an instance per line or separated by a comma or any symbol.

I'm talking about mastodon, but it should be the same for BlueSky (even if there isn't as many instances)

Describe alternatives you've considered

I don't see any alternatives as of right now.

[JoshyPHP]

For reference, I've just updated the docs with an example about discoverability. https://s9etextformatter.readthedocs.io/Plugins/MediaEmbed/Federated_sites/#discoverability

The ConfigurableHostInterface interface is new in 2.19.1, before that you'd have to check for AbstractConfigurableHostHelper or simply assume that any config with an helper attribute is configurable.

As far as UI goes, I recommend using a textarea for each federated/configurable site, that's what I do in XenForo.