Improve developer experience

[314eter]

There were some changes merged in #99 that make it more difficult to develop and test the parser locally or in forked repositories.

• By configuring and checking out the example repositories in the Github action instead of as git submodules, it becomes very impractical to parse the examples locally.
• Github actions should not only work on the master branch in the tree-sitter organization, but in forks and development branches too. That's were people will make their changes before opening a PR, and they should be able to test it.