add deprecation notice

README.md

@@ -2,11 +2,11 @@ NOTICE
 ======
 
 Active development of pyHealpix has stopped. The package will receive bug fixes
-if necessary, but otherwise the code has been integrated into the ducc0 package
-(https://gitlab.mpcdf.mpg.de/mtr/ducc), and further development is taking place
-there.
+if necessary, but otherwise the code has been integrated into the `ducc0`
+package (https://gitlab.mpcdf.mpg.de/mtr/ducc), and further development is
+taking place there.
 
-Please prefer ducc0 over pyHealpix if you are starting a new project!
+Please prefer `ducc0` over `pyHealpix` if you are starting a new project!
 
 
 pyHealpix - minimalistic Python interface for Healpix C++