The dotnet squad would like to improve the rule specification sprint
process requiring some UTs to be temporarily added under the rule folder
on RSPEC repository. These test case files (`.cs` and `.vb`) will be
copied to the sonar-dotnet repository during the initial phases of
implementation and will serve as an initial test bed.
However, before merging the PR on the RSPEC side we need to make sure
that these test case files are deleted and they don't end up on master.
The goal of this PR would be to add a check on the pipeline that will
fail if `.cs` or `.vb` files are detected (it's acceptable if it's red
until the implementation is done).
