cmake: allow config-mode Grantlee5 discovery from CMAKE_PREFIX_PATH (use Grantlee5Config.cmake if present)

cmake/FindGrantlee5.cmake

@@ -18,6 +18,16 @@ if (PKG_CONFIG_FOUND)
   endif()
 endif()
 
+# Try config-mode: look for Grantlee5Config.cmake in CMAKE_PREFIX_PATH or installed location
+find_file(_Grantlee5Config NAMES Grantlee5Config.cmake PATHS ${CMAKE_PREFIX_PATH} NO_DEFAULT_PATH PATH_SUFFIXES Grantlee5)
+if(_Grantlee5Config)
+  include(${_Grantlee5Config})
+  if(TARGET Grantlee5::Templates)
+    set(Grantlee5_FOUND TRUE)
+    return()
+  endif()
+endif()
+
 # Not found: provide helpful message and stop. Downstream CMakeLists check TARGET Grantlee5::Templates
 set(Grantlee5_FOUND FALSE)
 message(STATUS "Grantlee5 not found (shim cmake/FindGrantlee5.cmake); codegen_grantlee will be skipped if present.")