changeFontSize method
Implementation
void changeFontSize(double fontSize) {
final TextMetadata changedMetadata =
(metadata ?? RichTextEditorController.defaultMetadata).copyWith(
fontSize: fontSize,
);
changeStyleOnSelectionChange(
changedMetadata: changedMetadata,
change: TextMetadataChange.fontSize,
modifiedDeltas: deltas.copy,
selection: selection,
);
}