Introduce GitHub Actions

Things to check in actions:
1. **Bazel Build** - Check if Bazel is building is successful `bazel build -- //:...`
2. **[Buildifier](https://github.com/bazelbuild/buildtools/blob/master/buildifier/README.md)** - Check if Bazel files are following good practices. 
   - Files to include -> `*.bzl` + `WORKSPACE` + `.bazel`