1. Required to support a FULL screen mode for increase an area for editor & previewer 2. Required to add a vertical divider between editor & previewer to have ability to change width for both 3. Required to add a setting for initial PLANTUML diagram source text (right now is hardcoded with simple HELLO diagram) 4. Required to remove LEFT/RIGHT margin (5%) which decreases now a useful editor & preview areas. 5. Required to add an PLANTUML runtime syntax error checking, since at current moment diagram just stops a rendering without any notifications to user.
