[io grant] Document IO::Spec::*.devnull

Author: zoffixznet

doc/Type/IO/Spec/Unix.pod6

@@ -113,6 +113,18 @@ current directory and the "one directory up":
     my @dirs = <. foo .. bar>;
     say @dirs.grep(* eq $*SPEC.curupdir); # OUTPUT: «(foo bar)␤»
 
+=head2 method devnull
+
+Defined as:
+
+    method devnull(--> Str:D)
+
+Returns the string C<"/dev/null"> representing the
+L<"Null device"|https://en.wikipedia.org/wiki/Null_device>:
+
+=for code :skip-test
+    $*SPEC.devnull.IO.spurt: "blah blah";
+
 =head2 method tmpdir
 
 Defined as:

doc/Type/IO/Spec/Win32.pod6

@@ -93,6 +93,18 @@ that purpose.
     IO::Spec::Win32.catpath('E:', '', 'foo.txt').say;
     # OUTPUT: «E:foo.txt␤»
 
+=head2 method devnull
+
+Defined as:
+
+    method devnull(--> Str:D)
+
+Returns the string C<"nul"> representing the
+L<"Null device"|https://en.wikipedia.org/wiki/Null_device>:
+
+=for code :skip-test
+    $*SPEC.devnull.IO.spurt: "blah blah";
+
 =head2 method tmpdir
 
 Defined as: