feat: Library command

[sustained]

Any thoughts so far? For now I just decided to go with JSON files for storage.

We could make it so that people can add and modify libraries via commands and use a proper DB and everything but I think it's overkill. It's really not much work to add a JSON file for each library, in my eyes.

Heck large parts of it could be automated anyway if need be.

• Add LibraryService.
• Add !library command.
• Reduce info for now per request of gusto.
  • Reduce link overload.
  • Shorten descriptions.
• Add tons more libraries.
• Return similarly named libraries if no exact match or alias is found.
• 🚧 Add icons for major/noteworthy libraries/frameworks.
• Searching/filtering e.g. by tag etc.
• 🚫 A way to list all libraries (another blocked by util: Paginated embeds. #25).
• Anything I missed?

Future improvements (not this PR)

• Automated retrieval of latest version / release date for each library?
• Categories (use Vue Community + Awesome Vue's categories to help categorise).

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[sustained]

It's ugly but for now it works: https://github.com/sustained/vue-ecosystem-data

And by works I mean dumps tons of JSON files containing the data this command needs.

I think that constantly hitting the Github API makes no sense:

• it will slow down the !library command significantly
• we could potentially hit rate limits
• if there's an outage then the command is unusable
• it's not going to take particularly much memory to keep the libraries in memory
• this data rarely changes anyway, no need to hit the network constantly, we can just update the data on a schedule or something

[sustained]

Anyway, I can work on getting this feature finished now that I have all the data I need. Probably should be done in a day or two, one hopes. Then back to the !rfc and other features.