2016/twitter: Add 𝕏 (fka Twitter) auth to social auth providers

[dschwertfeger]

Description

Adds 𝕏 auth to social auth providers. Contributes to #2016 but doesn't fix it.

Closely modeled after #2110 (and #2212)

Select what type of change this PR introduces:

1. [ ] Just code/docs improvement (no functional change).
2. [ ] Bug fix (non-breaking change which fixes an issue).
3. [x] New feature (non-breaking change which adds functionality).
4. [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected).

Update Waspc ChangeLog and version if needed

If you did a bug fix, new feature, or breaking change, that affects waspc, make sure you satisfy the following:

1. [ ] I updated ChangeLog.md with description of the change this PR introduces.
2. [ ] I bumped waspc version in waspc.cabal to reflect changes I introduced, with regards to the version of the latest wasp release, if the bump was needed.

Update example apps if needed

If you did code changes and added a new feature or modified an existing feature, make sure you satisfy the following:

1. [x] I updated waspc/examples/todoApp as needed (updated modified feature or added new feature) and manually checked it works correctly.
2. [ ] I updated waspc/headless-test/examples/todoApp and its e2e tests as needed (updated modified feature and its tests or added new feature and new tests for it).

Note

• 11 e2e-tests still failing (seem to be mostly about checksums?)
• [x] Manually tested login with 𝕏 in todoApp