Improve dialog system

[JaXt0r]

The current implementation is just rudimentary ;-)

More implementation is needed:

• Subtitles (e.g. show them on top of their heads)
• Better align the dialog box canvas with an NPC (e.g. show it right/left of an NPC)
• Enter a dialog by clicking on the NPC
• Bonus: highlight NPC in brighter color if raycast/hand is pointing towards them like in original G1

Boundary:

• A few dialog options aren't handled correctly, as we have no proper NPC inventory so far. Feel free to skip it for now.