that's theoretically possible, but beyond the scope of the work we have planned in the near feature.

it's a great idea though - I will add it to the "Discussions" to track for the future. I can personally see the benefit of PostGIS support

Are you looking for contributions? Can I join the party?

yes, we'd love more contributors

I also wanted to ask about extensions. How does it work internally? Does it ask the database for parsing or does it have its own syntax analyzer?

we are using the actual Postgres server source to parse the sql file(s) into both an abstract- and a concrete syntax tree. Its bundled with the language server and therefore works standalone. We will add the option to connect to a database, but only to enable features such as autocompletion and code actions a la „Execute the statement under the cursor“.