Adds OAuth functionality, alternate token auth to HTTPClient

[alentoghostflame]

Summary

Give me time, I want this public so people can start seeing it and, if something happens to this PR, take the code in here and use it.

• Adds nextcord/oauth.py + OAuth2Endpoint
  • A class that provides a basic response and callback for oauth responses from Discord.
  • Uses an aiohttp.web.Application to host the site, but has a middleware that can be used by other solutions.
  • Can be ran alongside nextcord.Client/Bot, any other bot solution, or standalone.
• asdf

Checklist

• [X] If code changes were made then they have been tested.
  • [ ] I have updated the documentation to reflect the changes.
  • [ ] I have run task pyright and fixed the relevant issues.
• [ ] This PR fixes an issue.
• [X] This PR adds something new (e.g. new method or parameters).
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
• [ ] This PR is not a code change (e.g. documentation, README, ...)

[alentoghostflame]

Due to a bit of talking about this PR's scope on the Nextcord Discord server, I'm not sure if continuing to add this to NC would be correct, and instead this should be in a different package/library? Not sure, still very open for discussion.

[EmmmaTech]

My bad. I tried to cancel the reviews and GitHub for some reason put them through.