[PARSE BUG]: Contract assertions

[HaydenMichel8]

Problem description

https://cppreference.com/cpp/language/contracts

C++26 feature so may not be a priority.

C++ code that can't be parsed correctly (please double-check that https://robotpy.github.io/cxxheaderparser/ has the same error)

int num = 0;
void f() pre((num++, false));
f();