Add Concept Exercise: `magical-measurements`

[0xNeshi]

Towards #103

Scaffold https://github.com/exercism/cairo/blob/main/exercises/concept/magical-measurements

Instructions for the exercise are already given (see .docs/instructions.md). Follow the instructions yourself to implement all the other necessary (missing) files/tests/content.

TODO:

• [ ] use other implemented concept exercise metadata files for inspiration, e.g. https://github.com/exercism/cairo/tree/main/exercises/concept/lucians-luscious-lasagna
  • [x] instructions.md are already given
  • [ ] implement introduction.md
  • [ ] implement design.md
  • [ ] implement hints.md
• [ ] implement the example solution in .meta/exemplar.cairo
• [ ] implement the exercise stub at src/lib.cairo
• [ ] implement tests for the exercise at _tests/magicalmeasuremets.cairo
• [ ] replace <your_gh_username> placeholder with your actual GH username in .meta/config.json