DOM insert event support

[streamich]

• [ ] Support all beforeInput event types
  • [x] Insert from clipboard
  • [ ] Insert from composition
  • [x] Insert rich-text from clipboard
  • [x] Insert Peritext rich-text
  • [ ] Insert image
  • [ ] Insert DataTransfer, file
  • [ ] Support all beforeInput inline formatting events
  • [ ] Support all beforeInput block-level events
• [ ] Support compositionstart, compositionend, etc. events.
• [ ] Support drag'&'drop events.
  • [ ] Image drop.
  • [ ] URL drop.
  • [ ] Rich-text drop.
  • [ ] File drop.