Swiftweekly.github.io: Switch to GH Actions for CI

[jessesquires]

• [x] Remove .travis.yml
• [x] Add .github/workflows/ci.yml
• [x] Add danger API token to secrets, DANGER_GITHUB_API_TOKEN

This exact workflow should work:
https://github.com/jessesquires/jessesquires.com/blob/master/.github/workflows/ci.yml

[jessesquires]

@BasThomas @fassko it looks like travis-CI was broken on some recent PRs

This should be an easy/quick fix if we switch to GitHub Actions

[jessesquires]

I've added the DANGER_GITHUB_API_TOKEN to the repo secrets

(since we're using my bot 😄)

[fassko]

I moved most of my projects t Github Actions. So far so good.

[BasThomas]

Sure, let's do this 👍