Also give the main page a title.

Change-Id: I6db588a9454d90a5974de5446d58d709f84d1906
Reviewed-on: https://boringssl-review.googlesource.com/8020
Reviewed-by: Adam Langley <agl@google.com>

Initial fork from f2d678e6e8 (1.0.2 beta).

(This change contains substantial changes from the original and
effectively starts a new history.)