Improve workspaces experience (i3/sway-like)

[s373r]

• [x] Set fixed workspace count
• [ ] Bind hotkeys (e.g. Super+1 to switch to the first one)
• [x] Map application to specific applications to workspaces via an extension
• [x] Show workspace indicators
  • Highlight the current
  • Ideally, show associated icon to workspace (like at i3-bar)