Add support for ANSI color codes in titles & subtitles

[Euheimr]

Setting view.TitleColor overrides ANSI color codes contained in the titles. If TitleColor is not set (ColorDefault) and the title/subtitle contains ANSI colors - render them!

Here's an example using the following code:

package main

import (
	"errors"
	"github.com/awesome-gocui/gocui"
	"github.com/gdamore/tcell/v2"
	"log"
)

const (
	ESC   string = "\033"
	RESET string = ESC + "[0m"
	RED   string = ESC + "[31m"
	GREEN string = ESC + "[0;32m"
	BLUE  string = ESC + "[0;34m"
)

func layout(g *gocui.Gui) error {
	maxX, maxY := g.Size()

	// View1 => Using ANSI colors but with Title Color set
	view1, err := g.SetView("view1", 0, 0, maxX/3, maxY-1, 0)
	if err != nil && !errors.Is(err, gocui.ErrUnknownView) {
		return err
	}
	view1.Title = "View1: " + RED + "Test Title"
	view1.Subtitle = "Subtitle test"

	// Setting TitleColor overrides any ANSI colors within Title or Subtitle
	view1.TitleColor = gocui.Attribute(tcell.ColorAzure)

	// View2 => Using ANSI colors without setting TitleColor
	view2, err := g.SetView("view2", maxX/3+1, 0, maxX-1, maxY-1, 0)
	if err != nil && !errors.Is(err, gocui.ErrUnknownView) {
		return err
	}
	view2.Title = "View2: " + BLUE + "Title is blue " + RESET + "(" + GREEN + "this is green" + RESET + ")"
	view2.Subtitle = BLUE + "Subtitle is blue" + RESET

	return nil
}

func quit(g *gocui.Gui, v *gocui.View) error {
	return gocui.ErrQuit
}

func main() {
	app, err := gocui.NewGui(gocui.OutputTrue, true)
	if err != nil {
		log.Panicln(err)
	}
	defer app.Close()

	app.SetManagerFunc(layout)

	if err = app.SetKeybinding("", gocui.KeyCtrlC, gocui.ModNone, quit); err != nil {
		log.Panicln(err)
	}

	if err = app.MainLoop(); err != nil && !errors.Is(err, gocui.ErrQuit) {
		log.Panicln(err)
	}
}

Result: