fix: add license identifier to CMake file (#50)

Signed-off-by: Henry Schreiner <[email protected]>

Author: henryiii

src/cython_cmake/cmake/FindCython.cmake

@@ -41,6 +41,8 @@
 # limitations under the License.
 #=============================================================================
 
+# SPDX-License-Identifier: Apache-2.0
+
 # Use the Cython executable that lives next to the Python executable
 # if it is a local installation.
 if(Python_EXECUTABLE)

src/cython_cmake/cmake/UseCython.cmake

@@ -70,6 +70,8 @@
 # limitations under the License.
 #=============================================================================
 
+# SPDX-License-Identifier: Apache-2.0
+
 if(CMAKE_VERSION VERSION_LESS "3.8")
   # CMake 3.7 required for DEPFILE
   # CMake 3.8 required for COMMAND_EXPAND_LISTS