Parse HEX colors to tui-rs' Rgb colors.
#C3F111
-> Color::Rgb(195,241,17)
#CFB
-> Color::Rgb(204,255,187)
142
-> Color::Indexed(142)
```rust
sruct ColorStruct {
#[serde(with = "colortotui"]
color: tui::style::Color,
#[serde(with = "colortotui::optional"]
optional_color: Option
let colortext = r###"{ "color" : "#12FC1C", "optionalcolor" : "123" }"###
let t: ColorStruct = serdejson::fromstr::
let c = ColorStruct {
color: Color::Rgb(18, 252, 28),
optional_color: Option assert_eq!(t, c);
```