Add repository's web page's URL to read-me file.
Post final draft of the proposal (first version).

* Use final ID syntax.
* Tweak date.
* Clean up wording.
* Change the author's note for "apply" from threading concerns to
visitation order.
* Trim the author's note for section 23.3.2.D to how to get a
reference to the entire contained object.
* Remove effect for calling "operator()" or "at" for zero-sized
arrays.