Add support for Makoton/Widgit

[robpomeroy]

Suggestion from Mastodon.

I'd say Widgit ( https://www.widgit.com/ ) and/or Makaton ( https://makaton.org/ ) symbol support built in ought to be a given. The barrier to that would be that both organisations essentially operate on a commercial basis which limits including their symbol sets in a free (in either sense of the word) product.