Add light/dark single json files.

[superlemon57]

iSH has the ability to have light and dark palettes in a single json file. It would be nice to add it to the repo (or just explain how to to it in the README).
For exemple, I created a latte/mocha json file that works:

{
  "dark" : {
    "backgroundColor" : "#1e1e2e",
    "colorPaletteOverrides" : [
      "#45475a",
      "#f38ba8",
      "#a6e3a1",
      "#f9e2af",
      "#89b4fa",
      "#f5c2e7",
      "#94e2d5",
      "#bac2de",
      "#585b70",
      "#f38ba8",
      "#a6e3a1",
      "#f9e2af",
      "#89b4fa",
      "#f5c2e7",
      "#94e2d5",
      "#a6adc8"
    ],
    "cursorColor" : "#f5e0dc",
    "foregroundColor" : "#cdd6f4"
  },
  "light" : {
    "backgroundColor" : "#eff1f5",
    "colorPaletteOverrides" : [
      "#bcc0cc",
      "#d20f39",
      "#40a02b",
      "#df8e1d",
      "#1e66f5",
      "#ea76cb",
      "#179299",
      "#5c5f77",
      "#acb0be",
      "#d20f39",
      "#40a02b",
      "#df8e1d",
      "#1e66f5",
      "#ea76cb",
      "#179299",
      "#6c6f85"
    ],
    "cursorColor" : "#dc8a78",
    "foregroundColor" : "#4c4f69"
  },
  "version" : 1
}