Stunner - Move to the use of Offscreen Canvas and Web Workers

There are different areas that work can be done in parallel execution, on a non DOM context, by moving to the use of OffscreenCanvas and WebWorkers API.

Some of the potential areas to be refactored are:

• Scratchpad/s
• Shape / canvas indexation (eg:Pickers,ColorMap)
• Align&Distribute
• Transferable image context (rendering) from offset to main canvas
  • Image strips
  • Text labels