📝(self-hosted) add documentation for self-hosting on docker compose

It describes the minimalist LaSuite Meet instance, with the simple
feature of having a room conference.

env.d/production.dist/postgresql

@@ -0,0 +1,11 @@
+# App database configuration
+DB_HOST=postgresql
+DB_NAME=meet
+DB_USER=meet
+DB_PASSWORD=<generate a secure password>
+DB_PORT=5432
+
+# Postgresql db container configuration
+POSTGRES_DB=meet
+POSTGRES_USER=meet
+POSTGRES_PASSWORD=${DB_PASSWORD}