Documentation for lib/systems

Additionally:
- fix a typo in lib/default with the type hinting
- fix a likely breaking change with lib.rad-dev.genNonX86, as it was
returning an attrset instead of a list of attrsets
- rename var to cond in lib.rad-dev.genWrapper, to make it clearer that
a condition is expected

Signed-off-by: ahuston-0 <aliceghuston@gmail.com>

lib/default.nix

@@ -20,7 +20,7 @@
     # set: attrset to search
     #
     # type:
-    # mapGetAttr :: String -> Attrset -> [Any]
+    # mapGetAttr :: String -> AttrSet -> [Any]
     mapGetAttr = (attr: set: lib.mapAttrsToList (_: attrset: lib.getAttr attr attrset) set);
 
     # gets list of files and directories inside of a directory