meta: add msvc support

since bluelib is already cross-platform, this is mostly just adding
__declspec(dllexport) to the library functions.

cmake/FindBluelib.cmake

@@ -106,6 +106,10 @@ if (Bluelib_FOUND)
 				INTERFACE_INCLUDE_DIRECTORIES "${Bluelib_${component}_INCLUDE_DIR}")
 			target_compile_definitions(Bluelib::${component} INTERFACE _CRT_SECURE_NO_WARNINGS=1)
 
+			if (Bluelib_STATIC)
+				target_compile_definitions(Bluelib::${component} INTERFACE BLUELIB_STATIC=1)
+			endif ()
+
 			set_target_properties(Bluelib::${component} PROPERTIES
 				IMPORTED_LINK_INTERFACE_LANGUAGES "C"
 				IMPORTED_LOCATION "${Bluelib_${component}_LIBRARY}")