Add fmt version in CMake package config template

aidge_core-config.cmake.in

 @PACKAGE_INIT@
 
 include(CMakeFindDependencyMacro)
-find_dependency(fmt)
+find_dependency(fmt @FMT_VERSION@)
 find_dependency(Threads)
 set(AIDGE_REQUIRES_PYTHON @AIDGE_REQUIRES_PYTHON@)
 set(AIDGE_PYTHON_HAS_EMBED @AIDGE_PYTHON_HAS_EMBED@)