Adds things to index closes #2816

doc/Language/objects.pod6

@@ -83,6 +83,7 @@ and assign to the container it returned with the L<C<=>|=> operator.
 All objects support methods from class L<Mu|/type/Mu>, which is the type
 hierarchy root. All objects derive from C<Mu>.
 
+X<|Type objects>
 =head2 Type objects
 
 Types themselves are objects and you can get the I<type object> by
@@ -443,6 +444,7 @@ in different stages of initialization. Submethods of the same name from
 subclasses have not yet run, so you should not rely on potentially virtual
 method calls inside these methods.
 
+X<|Private methods>
 =head2 Private methods
 
 Methods with an exclamation mark C<!> before the method name are not callable
@@ -476,14 +478,15 @@ CATCH { default { put .^name ~ ":\n" ~ .Str } }
 
 Private methods are not inherited by subclasses.
 
+X<|Submethods>
 =head2 Submethods
 
-Submethods are public methods that are not inherited by subclasses. The name
-stems from the fact that they are semantically similar to subroutines.
+Submethods are public methods that will  not be inherited by subclasses. The
+name stems from the fact that they are semantically similar to subroutines.
 
 Submethods are useful for object construction and destruction tasks, as well
-as for tasks that are so specific to a certain type that subtypes must
-certainly override them.
+as for tasks that are so specific to a certain type that subtypes would
+certainly have to override them.
 
 For example, the L<default method new|/type/Mu#method_new> calls submethod
 C<BUILD> on each class in an L<inheritance|#Inheritance> chain: