Features needed before all blocks can become extensions

[cwillisf]

The extension system is missing some features that will be needed before we can convert all blocks packages into extensions.

Blocking

• Synchronous dynamic menus
  • Menu items defined by a function which must return items immediately (as opposed to calling a callback or returning a promise)
  • Related: Extensions dynamic menu #934
• Menus referring to sprites, costumes, sounds, etc. should handle object renaming
• Monitors
• C Blocks
  • Must support loop icon
• E Blocks
  • Must support text on the middle line
• Non-droppable menus
• Event-triggered hats

Not Blocking

• Blocks that can dynamically have/not have a "next statement" connection
  • See "Stop All" block