Make it more clear that there are more functions being generated

The initial brief, suggests that only a small number of functions are
generated. This is in part historical. Docs.rs version doesn't link
to sub-page link to avoid version confusions.

README.md

@@ -34,6 +34,9 @@ impl NewStructName {
     ) -> NewStructName { ... }
     fn borrow_owner<'a>(&'a self) -> &'a Owner { ... }
     fn borrow_dependent<'a>(&'a self) -> &'a Dependent<'a> { ... }
+    [...]
+    // See the macro level documentation for a list of all generated functions
+    // https://docs.rs/self_cell/latest/self_cell/macro.self_cell.html#generated-api.
 }
 
 impl Debug for NewStructName { ... }

src/lib.rs

@@ -31,6 +31,9 @@
 //!     ) -> NewStructName { ... }
 //!     fn borrow_owner<'a>(&'a self) -> &'a Owner { ... }
 //!     fn borrow_dependent<'a>(&'a self) -> &'a Dependent<'a> { ... }
+//!     [...]
+//!     // See the macro level documentation for a list of all generated functions,
+//!     // section "Generated API".
 //! }
 //!
 //! impl Debug for NewStructName { ... }