rename fields to improve understanding, adapting maintenance.py (intermediate)

games/library/libpng.md

@@ -4,11 +4,11 @@ _libpng is the official PNG reference library._
 
 - Home: http://libpng.org/pub/png/libpng.html
 - Media: https://en.wikipedia.org/wiki/Libpng
-- Download: see home
+- Download: (see home)
 - State: mature
 - Keywords: official
-- Code: https://sourceforge.net/p/libpng/code/ci/master/tree/
-- Language(s): C
+- Code repository: https://sourceforge.net/p/libpng/code/ci/master/tree/
+- Code language: C
 - Code license: Special
 - Code license details: [libpng](https://sourceforge.net/p/libpng/code/ci/master/tree/LICENSE)