Re-add zef module installer

Author: ugexe

META.list

@@ -508,3 +508,4 @@ https://raw.githubusercontent.com/jonathanstowe/IO-Path-Mode/master/META.info
 https://raw.githubusercontent.com/hoelzro/p6-native-resources/master/META.info
 https://raw.githubusercontent.com/goneri/p6-Email-Notmuch/master/META.info
 https://raw.githubusercontent.com/jnthn/p6-concurrent-iterator/master/META.info
+https://raw.githubusercontent.com/ugexe/zef/master/META6.json