Address a couple miscellaneous issues

[ahlec]

This PR focuses on fixing up a couple of tiny issues:

• Add the same file header to each file. I created some new files, but didn't copy over the license header. I've added or changed the file header for every Python file to match now;
• Changed mecab.arm file permissions. Whenever I run the plugin on an M1 Mac, it changes the permissions for this file, which produces a git change. I committed this change so that developers don't need to see this change when running their code.
  • /support/mecab is already at this -rwxr-xr-x permission level, so it felt OK to commit this
• Fixed the mypy errors in all of the files. There were a couple of linting errors in the source files, mostly around typing. I've updated these to make the errors go away.
  • There is one issue with mypy that I wasn't able to fix in this PR. I've opened Repository restructure to fix mypy issues? #22 for discussion.

I've tested these changes on both Anki 2.1.54 and Anki 2.1.49.

Also, I wasn't sure (this is my first open-source project) if I should continue to maintain my fork, or push branches on this one now that I'm a contributor. If it wasn't OK for me to push to this repo, I'll continue to use my fork for any future work!

[obynio]

Hello, sorry for the late answer. Yeah seems like good changes, we can merge that !

this is my first open-source project

Well as far as I can see you make quality contributions !
It's a small open-source project but what matters is the fun we get doing it 🙂

Also I wasn't sure if I should continue to maintain my fork, or push branches on this one now that I'm a contributor.

You can push branches here or use your own project. Choose what's the more convenient for you 👍