feat(web/panettone): Add dev helpers for postgres db

Add a docker-compose file and lorri-based direnv for aiding in
running and connecting to a postgres database during development of
panettone.

Change-Id: I319eee52b52cd48e1f3d2e32c558989768dc19d8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1465
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: eta <eta@theta.eu.org>

web/panettone/shell.nix

@@ -0,0 +1,15 @@
+{ depot ? import ../.. {} }:
+
+with depot.third_party;
+
+mkShell {
+  buildInputs = [
+    docker-compose
+    postgresql
+  ];
+
+  PGPASSWORD = "password";
+  PGHOST = "localhost";
+  PGUSER = "panettone";
+  PGDATABASE = "panettone";
+}