STL: Include stl.natvis in this repository

[KindDragon]

Natvis file should be in that repository and linked to pdb file (/natvis)
Example:
https://github.com/microsoft/GSL/blob/7e99e76c9761d0d0b0848b91f8648830670ee872/CMakeLists.txt#L79-L81

Also, natstepfilter and natjmc file could be also useful

[StephanTLavavej]

I agree! We should work with the IDE team to make this possible. (Testing stl.natvis is currently the most significant issue to resolve here, as I understand it.)