dec method
Implementation
TextStyle? dec(int? dec) {
if (dec == 0) return this;
if (dec == 1) return this?.copyWith(decoration: TextDecoration.underline);
if (dec == 2) return this?.copyWith(decoration: TextDecoration.overline);
if (dec == 3) return this?.copyWith(decoration: TextDecoration.lineThrough);
return this;
}