Add shortcut for New note, improve Command palette

[penge]

• Adding a new keyboard shortcut (Ctrl/Cmd + Shift + I) to create a New note
• Adding an alternative way to toggle Sidebar or Toolbar via the Command palette
• Fixed "Repeat last command"
• Command palette tweaks:
  • Lighter color on mouse hover (to easily distinguish mouse or keyboard activated list item)
  • Automatically activated list item on mouse hover (so can easily continue using arrow keys from that point if needed)
  • Using a better color for Command palette input in Dark mode

Closes https://github.com/penge/my-notes/issues/345 Closes https://github.com/penge/my-notes/issues/368