Add more Discord libs to `!docs`

[vcokltfre]

I propose we add more Discord libraries to the !docs command, now that they are growing in popularity and being used in place of the outdated discord.py

The libs I propose are added are:

• disnake
• hikari
• nextcord

Why not py-cord?

Pycord provides - without the ability to disable - components in the discord namespace (including in sphinx), which would lead to collisions with the OG discord.py

[Akarys42]

Do we know if their sphynx symbols actually use the discord namespace?

[vcokltfre]

Pycord does, I've checked nextcord and it doesn't, so it should also be fine to add (I'll update my initial comment)

[onerandomusername]

py-cord does: https://docs.pycord.dev/en/master/

[mbaruh]

Was actioned shortly after the conversation.

[onerandomusername]

Was hikari added?