PostgREST version

[m0ast]

Improve documentation

Hello,
I didn't want to pollute #1811 so I made a new one. Actually, it's pretty much the same issue, which is to provide an easy way to get the used PostgREST version.

[steve-chavez]

This can be obtained right now by doing an http request directly to PostgREST(check the bash API docs for examples). Basically:

curl -s -I 'https://<project>.supabase.co/rest/v1/' | grep server

server: postgrest/20210627 ## which is a nightly version

[m0ast]

thank you steve