Implement the exercise "isbn-verifier"

[KevDi]

Implementation of the Exercise ISBN-Verifier. This is my first Exercise which i ported to the CPP Track. If wanted i will port more exercises to the CPP Track

[siebenschlaefer]

Most of it looks good to me. I checked the tests cases (isbn_verifier_test.cpp and tests.toml), they are an exact translation of the canonical-data.json. The solution seems to be correct (except for one small detail in a regular expression). I did not check whether the config.json is correct.

[KevDi]

First of all thanks for the feedback. @siebenschlaefer I think most of the points are because i first did my solution in the isbn_verifier.h/.cpp files and then copied everything to the example.h/.cpp. Is there a better way? Did you manipulate the CMakeList.txt and include the example files there or did you something different? Also i will fix the mentioned points. And put them up again.

[siebenschlaefer]

Looks good to me. Now let's wait for the maintainers.

Is there a better way?

I don't know. There's some tooling that performs validation checks but I never got that to work on my machine. Usually I just hope that @patricksjackson and the other maintainers will perform those integration and system-level tests.

[KevDi]

I moved here also the Example Files to the .meta Folder