feat: laser tool

[Kneemund]

Adds a laser pointer to the tool pen that produces stylized and temporary strokes with a constant width. The strokes fade out after lifting the pen (using animation frames), and fully disappear after a fixed amount of time (currently 1s).

• Closes Laser tool? (feature request) #476 / Add a laser pointer #1062.
• Depends on feat: animation events #1276.

Things to Discuss

• Changing stylistic choices (colors, widths, durations, ...).
  • Using a non-linear fade animation instead of the current linear one.
  • Waiting a few milliseconds before starting the fade animation.
• The tool currently uses an icon from icon library. It's supposed to depict CDs and lasers, but I'm not a huge fan. Can't find/think of a better icon though.