add & improve tiling window manager

[serapath]

@todo

• fix styling bug
• first draft can be non-resizable
• remove left/right/both buttons
• it splits the screen into editor (left), contract ui (right), menu bar (bottom)
• org-page#2: Play brand book / design guide
• play-ed#3: theme & styleguide
• smartcontract.codes#5: theme & styleguide
• fix responsiveness
• extend the concept to make it more feature rich into a new issue
  • window manager" to coordinate layout and communication between parts of the play-editor and surrounding components (iframes?), also of different workshops, etc...
  • make window manager (changable layout)
• when you embed you can pre-define what will be collapsed/expanded in

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