pgsql: Rework SQL/JSON documentation - Mailing list pgsql-committers

Rework SQL/JSON documentation

This makes the documentation conform more closely the style of other
function sections.

Includes suggestions from Erik Rijkers, Alvaro Herrera, and Justin
Pryzby.

Discussion: https://postgr.es/m/CAKFQuwaq5Ny6d3nWbJo=QO4RmhSk9JD8zrkURLR-wWmB2Pkz7Q@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a1e7616d6e1e8056b6eae6d68be9e1e658afaf96

Modified Files
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doc/src/sgml/func.sgml | 2642 +++++++++++-------------------------------------
1 file changed, 580 insertions(+), 2062 deletions(-)