✨ (concepts) Add concept exercise `interest-is-interesting`

[devkabiir]

This is inspired by the same on csharp track. Provides introduction to while loops & floating point numbers.

[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.