link Postgres docs when inserting SQL template from DB object tree context menu

[eug3nix]

Per feedback from peer-review, it may be useful to link PostgreSQL documentation in templates inserted from DB object tree context menu.
For example:

VACUUM
--FULL
--FREEZE
--ANALYZE
--DISABLE_PAGE_SKIPPING
--SKIP_LOCKED
--INDEX_CLEANUP
--TRUNCATE
--PARALLEL number_of_parallel_workers
public.categories
--(column_name, [, ...])

The simplest thing to do here is to add a comment with the docs link, a better way would be to mark such doc links in some way and recognize them in AceEditor to be rendered using a custom widget, make link in the comment clickable etc.