✨ (concept) Add new concept exercise `cars-assemble`

[devkabiir]

This is inspired by the same in csharp track. Provides a gentle introduction to variable assignment, if-statements and numbers.

[MatthijsBlom]

@devkabiir I don't think there is a need for force-pushes. The commits will probably be squashed at the end anyway. On the other hand force-pushes make it slightly harder for observers to follow developments in the PR.

[senekor]

The author of this PR has stopped responding in the discussions planning the work on the syllabus. But there's been a lot of work put into reviews already, so I'm keeping it open in case it can be salvaged in a future attempt to create a good syllabus.