Getting a list of available extensions

[s0lst1ce]

My feature request is about

• A new feature

Description of the solution I'd like
Sometimes you want to load all extensions but you don't necessarily know/remember which are available. Thus getting a list of such extensions would be nice.

Alternatives I've considered
Modifying the ls command would also do the trick. Having it show all extensions with its status (loaded or not) would be very useful. This could be done using the enabled_exts.json file since it's meant to contain all extensions.
This would also look nicer in an embed with different categories like loaded & available. This could also be the occasion to add a "loaded" timestamp in the file. Like this one could how much time elapsed since the last update.

What needs to be done

• Add a way to get a list of all extensions, no matter their state
• Make it an embed
• Update the documentation
• Add a "loaded" timestamp

[s0lst1ce]

Chose not to implement timestamps after all. This is not really useful since the update functions won't use it after all.
This feature is thus marked done with 718913c