First draft of PG 17 release notes

I have committed the first draft of the PG 17 release notes;  you can
see the results here:

    https://momjian.us/pgsql_docs/release-17.html

It will be improved until the final release.  The item count is 188,
which is similar to recent releases:

    release-10:  189
    release-11:  170
    release-12:  180
    release-13:  178
    release-14:  220
    release-15:  184
    release-16:  206
    release-17:  188

I welcome feedback.  For some reason it was an easier job than usual.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Only you can decide what is important to you.