usability

I did not realize that, when I recategorized those files. But you're right. (this also affects other images of sign language spellings, e.g. the BSL or Auslang).

And those files are still easily editable to add the missing letters. In fact they could as well be generated with a custom fonts, mapping the ASCII letters, but then they do not add any value for the sign language themselves that are not just a direct spelling of Basic English, i.e. just another form of the Basic Latin alphabet: we don't need any translator to generate these forms automatically for any word in many Latin-written language.