hiscore: gnw_dkjr: Donkey Kong Jr (New Wide Screen)

[udance4ever]

Support for saving hi scores (game A and B) for Game & Watch Donkey Kong Jr. using hiscore plugin.

Tested in Batocera Linux v39 (MAME v0.261)

EDIT: this is my first contribution - I read the documentation and could get more input as to the best way to add other Game & Watch driver updates to hiscore.dat as I complete & validate them. Should I just keep adding commits to this branch until it is merged (what I’m planning to do as I don’t expect this pull request to be processed immediately) or create separate pull requests?