Display: Add ansi escape code for colored and styled underlines

[icewolfz]

• 58 Set underline color - Not in standard; implemented in Kitty, VTE, mintty, and iTerm2 Next arguments are 5;n or 2;r;g;b
  • 5;n is xterm 256 color code
  • r,g,b are 0 to 255, see 38/48;2;r;g;b param code
• 59 Default underline color - Not in standard; implemented in Kitty, VTE, mintty, and iTerm2

This is possible using the css text-decoration-color property, but requires recoding the parser and expanding the format data type to track underline color as a separate property

[icewolfz]

see https://en.wikipedia.org/wiki/ANSI_escape_code

[icewolfz]

css color effects all styles, overline, underline, and strike though so if a block has all effects all of it would be colored but for the 2nd double underline as that is a custom border as text-decoration-style can no be used for the same reason color may not be able to, unless i allow this to effect all 3 and double underline

[icewolfz]

see https://sw.kovidgoyal.net/kitty/underlines/ for more