message: docs: add a note about the new imported target name for CMake
diff: @@ -2156,6 +2156,9 @@ Maintenance release. Changes:
  . Fix Wzero-as-null-pointer-constant warnings in pugixml.hpp
  . Work around several static analysis false positives
  +* Build system changes
  + . The CMake package for pugixml now provides a `pugixml::pugixml` target rather than a `pugixml` target. A compatibility `pugixml` target is provided if at least version 1.11 is not requested.
  +
  [[v1.10]]
  === v1.10 ^2019-09-15^
  