Add Readme for CI

Author: oleksiilevzhynskyi

.github/workflows/Readme.md

@@ -0,0 +1,9 @@
+# CI powered by GitHub Actions
+
+## Release
+
+For each tag `v*` that is pushed into `master` branch CI creates ["Release"](https://github.com/grammarly/focal/releases) and attaches package tarball `grammarly-focal-v*.tgz`. For details see `release.yml`
+
+## Tests
+
+For each push into pull_reusets CI runs tests. Check `tests.yml` for details.