[conan-center-index] Checks for semantic errors #182

It would be nice if there was the addition of two new checks, thought I am not sure where they would go in the hooks.

1. usage of self.requires.add which should not have the last add portion
2. usage of tools.check_min_cppstd should always have a preceding if self.settings.get_safe("compiler.cppstd"):

I am sure there are other "bad practices" which could be added but these two are very common looking at older recipes, next time they get update it will be more complete.