Added docs for Map.Capture

Author: Jan-Olof Hendig

doc/Type/Map.pod6

@@ -219,4 +219,26 @@ Returns C<True> if the invocant contains at least one key/value pair.
     my $m = Map.new('a' => 2, 'b' => 17);
     say $m.Bool;                                      # True
 
+=head2 method Capture
+
+Defined as:
+
+    method Capture(Map:D:) returns Capture:D
+
+Usage:
+
+    MAP.Capture
+
+Returns a L<Capture|/type/Capture> where each key, if any, has been converted
+to a named argument with the same value as it had in the original C<Map>.
+The returned C<Capture> will not contain any positional arguments.
+
+    my $map = Map.new('a' => 2, 'b' => 17);
+    my $capture = $map.Capture;
+    my-sub(|$capture);                                # 2, 17
+
+    sub my-sub(:$a, :$b) {
+        say "$a, $b"
+    }
+
 =end pod