Update coupling guidance in online docs to make FTorch REQUIRED when …

…coupling in CMake.

pages/cmake.md

@@ -112,7 +112,7 @@ If doing this you need to include the following in the `CMakeLists.txt` file to
 find the FTorch installation and link it to the executable.
 
 ```CMake
-find_package(FTorch)
+find_package(FTorch REQUIRED)
 target_link_libraries( <executable> PRIVATE FTorch::ftorch )
 message(STATUS "Building with Fortran PyTorch coupling")
 ```