func (t *SimpleStyledText) RegisterStyle(r rune, style tcell.Style) {
	if r == 'N' {
		t.Text.SetStyle(style)
	}
	if unicode.IsLetter(r) {
		t.styles[r] = style
	}
}
Registers a style for the given rune.  This style will be used for
text marked with %<r>. See SetMarkup() for more detail.  Note that
this must be done before using any of the styles with SetMarkup().
Only letters may be used when registering styles, and be advised that
the system may have predefined uses for upper case letters.
package views
import (
	"github.com/gdamore/tcell"
	"unicode"
)
type SimpleStyledText struct {
	styles map[rune]tcell.Style
	markup []rune
	Text
}
func (t *SimpleStyledText) SetMarkup(s string) {
	markup := []rune(s)
	styl := make([]tcell.Style, 0, len(markup))
	text := make([]rune, 0, len(markup))
	style := t.styles['N']
	esc := false
	for _, r := range markup {
		if esc {
			esc = false
			switch r {
			case '%':
				text = append(text, '%')
				styl = append(styl, style)
			default:
				style = t.styles[r]
			}
			continue
		}
		switch r {
		case '%':
			esc = true
			continue
		default:
			text = append(text, r)
			styl = append(styl, style)
		}
	}
	t.Text.SetText(string(text))
	for i, s := range styl {
		t.SetStyleAt(i, s)
	}
	t.markup = markup
}