Add CI/CD pipelines with Github Actions

[baruchiro]

We need to add CI/CD pipelines using Github Actions. The pipeline should test any pull request before it is merged. Additionally, it should publish a new version whenever there is a push to the master branch (see #4).

This extension consists of 356 files, out of which 249 are JavaScript files. For performance reasons, you should bundle your extension: https://aka.ms/vscode-bundle-extension . You should also exclude unnecessary files by adding them to your .vscodeignore: https://aka.ms/vscode-vscodeignore