[SuperEditor] - Create a request for typing text

[matthew-carroll]

Typing text involves (maybe) deleting an expanded selection, inserting the text, and then updating the selection position.

Create a request that does all of these things.

Example of what is currently required to do this:

  editor.execute([
      if (!selection.isCollapsed) //
        DeleteContentRequest(
          documentRange: selection.normalize(widget.editor.context.document),
        ),
      InsertAttributedTextRequest(
        selection.base,
        text,
      ),
      ChangeSelectionRequest(
        DocumentSelection.collapsed(
          position: selection.base.copyWith(
            nodePosition: TextNodePosition(offset: (selection.base.nodePosition as TextNodePosition).offset + 1),
          ),
        ),
        SelectionChangeType.alteredContent,
        SelectionReason.userInteraction,
      ),
    ]);
  }