Help: Add notes for topic 'mingw-compile-features'

Help/release/dev/mingw-compile-features.rst

@@ -0,0 +1,6 @@
+mingw-compile-features
+----------------------
+
+* The :manual:`Compile Features <cmake-compile-features(7)>` functionality
+  is now aware of features supported by GNU compilers on Windows, versions
+  4.4 through 5.0.