setMargin(horizontal, vertical) {
      this.updateConfig('margin', { horizontal: horizontal, vertical: vertical })
    }
Sets the editor internal margins, and update the editor contents immediately to reflect this.
Margins provide a useful "click area" where the user can click to go to the beginning
or end of a line (or first or last line) without being super-precise about the click.
@apidoc Configuration
@param horizontal The horizontal (left-right) margins.
@param vertical The vertical (top-bottom) margins.
@returns {*}