Added multi-positional use of assuming (#1296)

Borrowed content from brian d foy's Stack Overflow post https://stackoverflow.com/a/43669837/215487

doc/Type/Callable.pod6

@@ -55,6 +55,28 @@ corresponding parameters.
 
     say &slow.assuming(10000000).&bench; # OUTPUT: «(10000000 7.5508834)␤»
 
+For a sub with arity greater than one, you can use C<Whatever> C<*> for all of the positional parameters that are not "assumed".
+
+    sub first-and-last ( $first, $last ) {
+        say "Name is $first $last";
+    }
+    
+    my &surnamed-smith = &first-and-last.assuming( *, 'Smith' );
+
+    &surnamed-smith.( 'Joe' ); # OUTPUT: «Name is Joe Smith␤»
+    
+You can handle any combination of assumed and not assumed positional parameters:
+
+    sub longer-names ( $first, $middle, $last, $suffix ) {
+        say "Name is $first $middle $last $suffix";
+    }
+
+    my &surnamed-public = &longer-names.assuming( *, *, 'Public', * );
+
+    &surnamed-public.( 'Joe', 'Q.', 'Jr.'); # OUTPUT: «Name is Joe Q. Public Jr.␤»
+
+(Multi-parameter examples adapted from brian d foy's post https://stackoverflow.com/a/43669837/215487)
+
 =comment according to design docs it's Callable but in rakudo it's assuming is in Block
 
 =head1 Operators