Add workflow to test parse this plugin

[warp-core]

Copy-pasted from the data files check in endless-sky/endless-sky, with some edits as appropriate. Running on the PR now just to test that it runs, but we won't be able to run it on other PRs as it is because those will have @2x versions of images that do not exist in the base game, (that's generally the point of PRs here) and I can't tell it to check out the branch for the relevant PR to endless-sky/endless-sky.

[warp-core]

ARGH The test parse script uses the -p argument which doesn't load images or sounds, so this isn't going to be very useful until that is changed.