Add demo server

[steve-chavez]

Having a demo server would make our sample curl calls(https://github.com/PostgREST/postgrest-docs/pull/444) much more didactic(replacing localhost:3000 by api.postgrest.org).

Perhaps we can host it using a db-tx-end=rollback.

Previously discussed on https://github.com/PostgREST/postgrest-docs/issues/349#issuecomment-732063149

[steve-chavez]

Wolfgang's Hollywood schema could be a nice sample schema to showcase all the features.

[steve-chavez]

Some progress on this. I got a bare metal server from Hetzner Server Auction.

Specs:

CPU1: Intel(R) Xeon(R) CPU E3-1246 v3 @ 3.50GHz (Cores 8)
Memory:  31983 MB
Disk /dev/sda: 2000 GB (=> 1863 GiB) doesn't contain a valid partition table
Disk /dev/sdb: 2000 GB (=> 1863 GiB) doesn't contain a valid partition table
Total capacity 3726 GiB with 2 Disks

With unlimited traffic. All at the price of ~$28/month :tada:

Next step: install NixOS on it.

(32 GB RAM should be plenty for the traffic we might get, the two 2TB disks might come in handy for later when we render MVT tiles).