Add @-moz-document wrapper and metadata header to the main file

[Sepitus-exe]

After some deliberation, I decided that having a development file that differs from the officially released one is probably not a wise idea.

This will make a mess out of the spacing again, but I believe it's for the better we bite the bullet now, before the versions unexpectedly diverge in the future.

[Sepitus-exe]

Before doing so, I would like to make sure there aren't any unmerged branches, that might take an issue with such a drastic change. I will wait for you @wrex to give me the go-ahead.

[wrex]

I'm not following.

If the issue is two space or four space tabs, we just need to be consistent.

We are currently using 2 space.

I thought the stylus in-browser editor also had a setting for 2-space, but if you'd prefer to set it to four it's easy enough to add a vscode configuration file to the repository to use 4 (so I don't accidentally screw it up again)

This is how I have my stylus editor set up so I can just cut and paste without worrying about reformatting:

[Sepitus-exe]

Oh, looks like I made some incorrect assumptions. I thought introducing the @-moz-document domain("www.wanikani.com") would cause an additional layer of indentation, which seems to not be the case looking at the exported code from stylus.