FetchContent_Declare usage

[hsdk123]

Hi, it looks as if the headers inside the library aren't auto exposed when using FetchContent_Declare. This is a request to allow this to happen.

[ncoder-1]

I'm currently doing something like this:

FetchContent_Declare(
        csv
        GIT_REPOSITORY https://github.com/vincentlaucsb/csv-parser
        GIT_TAG 2.1.0.1
        GIT_SHALLOW TRUE
)
FetchContent_MakeAvailable(csv)
include_directories(${csv_SOURCE_DIR}/single_include)

Not sure if that's the right way, but it works.