Peritext context menu UI

[streamich]

• [x] Find best position for opening the first panel
• [x] Respect screen height
  • [x] Limit and add scrolling, if menu too tall
• [ ] Support arrow up/down (find elements and focus)
• [x] Detect from which side to best open nested panel
• [x] Open nested panels higher, when parent item low on screen
• [ ] a11y
• [ ] Show keyboard shortcut map
• [x] Children expansion
  • [x] Show big items in nested context panes
  • [x] Limit each section to the number specified in expand property
• [ ] Show "Formatting" expansion as a horizontal row of small icons
• [x] Support nested panels in search mode
• [ ] Test on various devices/borwsers
  • [ ] Windows
  • [ ] Firefox
  • [ ] Safari
  • [ ] Mobile
  • ...
• [x] Handle outside click
• [x] Create version an automatic popover version
• [x] Show nested panel on title hover
• [ ] Add tooltips
• [ ] Add big display tooltips (a la Notion)