Add a few more docs

Author: notriddle

src/doc/rustdoc/src/read-documentation/search.md

@@ -147,6 +147,7 @@ will match these queries:
 * `Read -> Result<Vec<u8>, Error>`
 * `Read -> Result<Error, Vec>`
 * `Read -> Result<Vec<u8>>`
+* `Read -> u8`
 
 But it *does not* match `Result<Vec, u8>` or `Result<u8<Vec>>`.
 
@@ -200,6 +201,11 @@ since parens act as the grouping operator. If they're empty, though, they will
 match both `unit` and `tuple`, and if there's more than one type (or a trailing
 or leading comma) it is the same as `primitive:tuple<...>`.
 
+However, since items can be left out of the query, `(T)` will still return
+results for types that match tuples, even though it also matches the type on
+its own. That is, `(u32)` matches `(u32,)` for the exact same reason that it
+also matches `Result<u32, Error>`.
+
 ### Limitations and quirks of type-based search
 
 Type-based search is still a buggy, experimental, work-in-progress feature.