Improve VS Code design resources in Figma

[kkbrooks]

Our Figma library is out of date, lacks documentation, and we've received feedback that its difficult for extension teams to use when designing their experience.

Areas to improve

• Add variables for spacing and corner radius
• Remove outdated color styles
• Rebuild controls with up-to-date features (auto layout, modes, etc)
  • Activity Bar
  • Chat
  • Dialogs
  • Editor
  • Extensions
  • Hovers
  • Input
  • Labels
  • List
  • Menu
  • Notebooks
  • Notifications
  • Peek Views
  • Panel
  • Progress
  • Quick Pick
  • Settings
  • Sidebar
  • Status bar
  • Suggest Widget
  • Tabs
  • Templates
  • Titlebar
  • Utilities
• Add relevant links to API documentation to each applicable control
• Redo Type, Colors, Icon page
• Redo README/intro page
• Republish to the community as a UI Kit