Add option to build library as a shared object.

I see currently library is being built as a static library. That makes every project that uses this library inject the code inside their program. Instead it can be built as a dynamic library (`.so` on linux and `.dll` on windows) and link dynamically on the runtime. It will reduce size of the result binaries and will get an option to users to update ittapi library without updating application (if the ABI is compatible).

My question is if it possible to add shared target to the build? It should be as easy as removing `STATIC` keyword from `add_library` and then it can be controlled with [BUILD_SHARED_LIBS](https://cmake.org/cmake/help/latest/variable/BUILD_SHARED_LIBS.html) argument. Or there is a reason why it can't be loaded as a shared library?