add wiki syntax
tweak warning messages

I felt they were a bit too agressive and would cause me some undue
stress. Now, they're still very visible, but not distracting.
fix some background color issues
add readme note about dark mode
tweak dark mode colors
add dark mode
usage instructions
change highlight color

I felt for a while that the mint was being slightly over-used when
having both searches and visual mode selections.
initial commit