This PR intends to add entrypoints and some smoke tests for `iswxdigit`
function
Changes made are :-
- Added entrypoint for `iswxdigit` in wctype.yaml
- Added CMake entrypoint object for `iswxdigit`
- Added Header and implementation in `iswxdigit.h` and `iswxdigit.cpp`
- Added test for `iswxdigit` in iswxdigit_test.cpp
- Added `iswxdigit` in entrypoints.txt for available platforms
Tested using = `ninja libc.test.src.wctype.iswxdigit_test.__unit__`
passes all tests
part of #185136
49d9ba9572