- For OEM modes where there is already a theme, add a preselect:
key to pick a specific theme and have that one come up as already-
selected in the list.
- Don't re-run the lnftool if an already-selected theme is clicked
again. Use toggled() instead of clicked().
- calculate a hash of the filename, and use that
- makes it possible to distinguish different screenshots
even when the image file is missing / badly configured
- most colors will be dreadful
