Move more non-source template files to CMake dir

CMake/glfw3.pc.in

@@ -0,0 +1,13 @@
+prefix=@CMAKE_INSTALL_PREFIX@
+exec_prefix=${prefix}
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+
+Name: GLFW
+Description: A multi-platform library for OpenGL, window and input
+Version: @GLFW_VERSION@
+URL: https://www.glfw.org/
+Requires.private: @GLFW_PKG_DEPS@
+Libs: -L${libdir} -l@GLFW_LIB_NAME@
+Libs.private: @GLFW_PKG_LIBS@
+Cflags: -I${includedir}

CMake/glfw3Config.cmake.in

@@ -0,0 +1,3 @@
+include(CMakeFindDependencyMacro)
+find_dependency(Threads)
+include("${CMAKE_CURRENT_LIST_DIR}/glfw3Targets.cmake")