First draft of PG 19 release notes

I have completed the first draft of the PG 19 release notes:

    https://www.postgresql.org/docs/devel/release-19.html

The feature count is 212.  The recent average is 200:

    https://momjian.us/main/writings/pgsql/missing.pdf#page=3

I will create a wiki page to explain my methods used to create this
because, someday, someone else will need to do this.

I am traveling April 19 to May 7, so I might not be able to make quick
adjustments based on feedback.  Another committer can handle them, or
you can wait for me to get to it.

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

  Do not let urgent matters crowd out time for investment in the future.