Make it easier to see defaults for Promise.keep/cause

Author: zoffixznet

doc/Type/Promise.pod6

@@ -222,8 +222,7 @@ creates a chained promise.
 
 =head2 method keep
 
-    multi method keep(Promise:D:)
-    multi method keep(Promise:D: \result)
+    multi method keep(Promise:D: \result = True)
 
 Keeps a promise, optionally setting the result. If no result is passed, the
 result will be C<True>.
@@ -242,8 +241,7 @@ taken. See method C<vow> for more information.
 
 =head2 method break
 
-    multi method break(Promise:D:)
-    multi method break(Promise:D: \cause)
+    multi method break(Promise:D: \cause = False)
 
 Breaks a promise, optionally setting the cause. If no cause is passed, the
 cause will be C<False>.