Patch ColorTag

[kechuan]

filter unformat HEXColor to prevent FormatException crash.

my Example:

BBCodeText(
data:"[color=#ffffff]test[/color] \n""[color=ffffff]test[/color] \n""[color=33ffffff]test[/color]"//typo"[color=RED]test[/color]", //otherReason
stylesheet:BBStylesheet(
tags: [PatchColorTag()],
)
)
...
//colorTagif(hexColorRegExp.hasMatch(hexColor)){
debugPrint("match it: $hexColor");
return oldStyle.copyWith(color:HexColor.fromHex(hexColor));
}

output:
flutter: match it: #ffffff
flutter: match it: ffffff