- Check if button element is available in the toolbox
- Add the button to the canvas
- Change button label and check reflection on the canvas

Remove warning for used-before-defined.

Newer versions removed some of the package.json variables. Almost the 
same can be achieved by using a config object.

The other one used some deprecated functionality. Also we have more 
control over what is happening now.

Based on TipTap which in turn is based on ProseMirror. No further assets 
are needed.

Also add release notes document.

                                                         [style.height.%]="100"