Support for `$` in grid cells

[puzzzlematt]

Dear Github,
My puzzle requires using the $ to be used as an answer to some of the squares in my puzzle (a I one direction and an S the other direction). Can you add the option to include $ as an entry option?
Thank you!
Matt Zeleznik

[mdirolf]

Renaming to keep the scope of this issue small. If you want to open a separate issue for supporting images in grid cells that's fine, though my honest answer is that image support is unlikely to happen any time unless somebody else takes it on and produces something that I think works well.

I think I'm on board with adding $ as a supported character, though we do have to be somewhat selective about what characters are allowed in grids as they each require an addition to the virtual keyboard.

[mdirolf]

See 18f24f3 for an example of how to add this