Add Mastodon as an oauth2 provider

[grahhnt]

What does this PR do?

This PR adds Mastodon oAuth2 support

Test Plan

I've created a test app that will attempt to login with the oAuth2 provider.

Related PRs and Issues

Closes #3878

Have you added your change to the Changelog?

I didn't make changes to the master branch, I don't think I need to modify that.

Have you read the Contributing Guidelines on issues?

Yes

[PineappleIOnic]

Thank you so much for the PR 🤩. We're adding the hacktoberfest-accepted label to ensure this PR counts towards your Hacktoberfest contributions count. With that said, please stay active on this PR to address any comments once you receive a review. Happy Hacktoberfest! 🎃

[christyjacob4]

@grahhnt thanks a lot for your contributions during Hacktoberfest 2022!

Please reach out to me on our Discord server if you would like to claim your Appwrite swags! As a way of saying thank you, we would also love to invite you to join the Appwrite organization on GitHub. Please share your GitHub username with us on Discord. 

This PR needs some more work ever since we moved the appwrite console to https://github.com/appwrite/console

You can take a look at this PR for reference appwrite/console#213

[h0lybyte]

Epic! I can not wait for this to be added!

[grahhnt]

I apologize but I don't have time to update this to the newer appwrite console. If someone else is able to take it, that would be great!