Add pronto CI

[Zethson]

Dear everyone,

this PR:

1. Cleans up the Github Actions workflow file. All of the comments are noise because the code speaks for itself in this case. (not always the case but here it is)
2. Adds a CI step that installs Pronto and ensures that the most important (am I correct here?) owl files are compatible with Pronto. Pronto is opinionated (to some extent) but it's widely used in the Python ecosystem and being compatible with it is important for users. It serves as a form of QC.
3. Removes the unused Travis CI config file.

[Zethson]

I can't properly test it because your settings restrict the CI to be automatically run.