preparedOracleText method
Returns a visual representation of the oracleText using SVGs wrapped in
a WidgetSpan for valid MTG symbols.
Returns null if oracleText is null. If it doesn't contain any valid
MTG symbols, will return a TextSpan with the original oracleText.
Implementation
TextSpan? preparedOracleText() => _preparedOracleText(oracleText);