Add vcpkg installation instructions

[PhoebeHui]

yajl is available as a port in VCPKG , documenting the install process here will help users get started by providing a single set of commands to build yajl, ready to be included in their projects.

VCPKG is a C++ library manager that simplifies installation for yajl and other project dependencies, we also test whether our library ports build in various configurations (dynamic, static) on various platforms (OSX, Linux, Windows: x86, x64, UWP, ARM) to keep a wide coverage for users.

I'm a maintainer for vcpkg, and here is what the port script looks like. We try to keep the library maintained as close as possible to the original library.

[CreatorSergey]

hi, @PhoebeHui!

i try to use vcpkg in cmake for yajl

find_package(yajl CONFIG REQUIRED)
target_link_libraries(my_project PRIVATE yajl_s)

but it is cant find package. Do you have some instructions to use yajl with cmake ?

[PhoebeHui]

@CreatorSergey, sorry for late response!

Yajl doesn't export cmake config and target file, so you can't find the package via find_package, you can use find_path and find_library instead. See https://github.com/microsoft/vcpkg-docs/blob/main/vcpkg/examples/installing-and-using-packages.md?plain=1#LL183C1-L183C1