Doc: make an editing pass over the v12 release notes.
Copy-edit or rewrite some items, add some items that I thought
deserved documenting, remove some others that didn't (notably,
I'm not on board with documenting documentation changes), fix
some poorly-pointed links, move some items to other sections,
etc etc.
Branch
------
REL_12_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/b6a4d0498757a6e345e07b2a84eb8333f5e5235e
Modified Files
--------------
doc/src/sgml/release-12.sgml | 1177 ++++++++++++++++++++++--------------------
1 file changed, 615 insertions(+), 562 deletions(-)
