Add example for wildcard template maching in the docs

Author: Discookie

clang-tools-extra/docs/clang-tidy/checks/bugprone/unsafe-functions.rst

@@ -118,9 +118,13 @@ fully qualified name (``::std::original``).
 
    Fully qualified names can contain template parameters on certain C++ classes, but not on C++ functions.
    Type aliases are resolved before matching.
+
    As an example, the member function ``open`` in the class ``std::ifstream``
    has a fully qualified name of ``::std::basic_ifstream<char>::open``.
 
+   The example could also be matched with the regex ``::std::basic_ifstream<[^>]*>::open``, which matches all potential
+   template parameters, but does not match nested template classes.
+
 Options
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