Allow specific file paths in `includePath` and `browse.path` from a custom provider and `c_cpp_properties.json`

[icebox-test]

Hello,
currently only folders can be specified in browse.path and includePath.
This leads to issues in bigger projects that contain smaller sub-projects.

project
├───common_include
│   ├───foo.h
│   └───bar.h
├───target_include
│   ├───foo.h
│   └───bar.h
└───main.c

As an example, here only common_include/foo.h and target_include/bar.h are required but as only folders can be defined via browse.path and includePath both */foo.h and */bar.h files will be parsed.

This may be solved by using compile_commands.json files however this is not possible in my case.
I know all the correct files that should be used in IntelliSense however I'm unable to define them as these

browse.path: Path is not a directory: c:\path\to\common_include\foo.h
includePath: Path is not a directory: c:\path\to\target_include\bar.h

errors are raised while entering specific files (applies to both .h and .c files).

At the same time forcedInclude allows to define specific files that should be included.

Would it be possible to allow specific files to also be defined in the other settings in the c_cpp_properties.json file and by a custom provider?