Give minimal info about methods for Positional/Associative roles

We should at least mention the methods that *must* be implemented.
And we should refer to the extended information: since I had no clue
as to how to properly refer to this internal information in a link,
I've just use the URL (which apperently happens more often).  If this
is incorrect, please fix  :-)

doc/Type/Associative.pod6

@@ -66,6 +66,23 @@ you use the parametrized version of Associative.
     my %any-hash;
     %any-hash.keyof; #OUTPUT: «(Str(Any))␤»
 
+=head1 Methods that should be provided
+
+=head2 method AT-KEY
+
+    method AT-KEY(key) { }
+
+Should return the value / container at the given key.
+
+=head2 method EXISTS-KEY
+
+    method EXISTS-KEY(key) { }
+
+Should return a C<Bool> indicating whether the given key actually has a value.  
+
+=head1 See also
+
+See L<Methods to implement for positional subscripting|https://docs.perl6.org/language/subscripts#Methods_to_implement_for_associative_subscripting> for information about additional methods that can be implemented for the C<Associative> role.
 
 =end pod
 

doc/Type/Positional.pod6

@@ -19,6 +19,31 @@ include L<List>, L<Array>, L<Range>, and L<Buf>.
 Returns the type constraint for elements of the positional container. Defaults
 to L<Mu>.
 
+=head1 Methods that should be provided
+
+=head2 method elems
+
+    method elems() { }
+
+Should return the number of available elements in the instantiated object.
+
+=head2 method AT-POS
+
+    method AT-POS(position) { }
+
+Should return the value / container at the given position.
+
+=head2 method EXISTS-POS
+
+    method EXISTS-POS(position) { }
+
+Should return a C<Bool> indicating whether the given position actually has a
+value.
+
+=head1 See also
+
+See L<Methods to implement for positional subscripting|https://docs.perl6.org/language/subscripts#Methods_to_implement_for_positional_subscripting> for information about additional methods that can be implemented for the C<Positional> role.
+
 =end pod
 
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