fix: Remove appveyor and travis and use Github actions for tests

[ashleygwilliams]

🤕 do not merge 🤕

fixes #594

[palfrey]

How's this going? Are you interested in patches to fix any of the current issues here?

[azriel91]

Heya @drager, I think the last CI failure can be fixed with the following changes (see example diff, which I've tacked on top of #851):

• Updating wasm-bindgen-test expected version to 0.3.24 in tests/all/lockfile.rs

• Removing the and(contains("[INFO]: Installing wasm-bindgen...")) line from tests/all/log_level.rs

  I suspect the Cache implementation means wasm-bindgen isn't installed multiple times across tests, so this line is not output.

[drager]

Heya @drager, I think the last CI failure can be fixed with the following changes (see example diff, which I've tacked on top of #851):

* Updating `wasm-bindgen-test` expected version to `0.3.24` in `tests/all/lockfile.rs`

* Removing the `and(contains("[INFO]: Installing wasm-bindgen..."))` line from `tests/all/log_level.rs`
  I suspect the `Cache` implementation means `wasm-bindgen` isn't installed multiple times across tests, so this line is not output.

Thanks, I'm merging your PR now!