doc: Improve config docs

apps/docs/configuration/reference.mdx

@@ -0,0 +1,39 @@
+---
+title: Configuration Reference
+---
+
+At the moment, Postiz is entirely configured by environment variables. It is 
+important to understand that any configuration change to environment variables
+will require an application restart.
+
+An example file of the most used configuration settings can be found here; [example postiz.env file](https://raw.githubusercontent.com/gitroomhq/postiz-app/main/.env.example)
+
+## Required Settings
+
+### `DATABASE_URL`
+
+eg: `postgresql://postiz-user:postiz-password@localhost:5432/postiz-db-local`
+
+Postgres is not strictly necessary, Postiz uses Prisma to connect to the database, so technically mariadb or other databases could be used.
+
+### `REDIS_URL`
+
+eg: `redis://localhost:6379`
+
+### `JWT_SECRET`
+
+A random string that should be unique for every installation, this is used to secure your JWT auth tokens.
+
+### `FRONTEND_URL`
+
+eg: `http://postiz.example.lan:4200`
+
+### `NEXT_PUBLIC_BACKEND_URL`
+
+eg: `http://postiz.example.lan:3000`
+
+### `BACKEND_INTERNAL_URL`
+
+If running everything in the same host/container: `http://localhost:3000`
+
+