show info about dirs in readme file

Signed-off-by: greatbridf <greatbridf@icloud.com>

README.md

@@ -21,3 +21,9 @@ or you can use docker compose:
 ```shell
 docker-compose up -d
 ```
+
+# Directories explained
+
+- `conf`: This is the place where your config of caddy resides
+- `data`: Caddy will store TLS certs and etc here.
+- `log`: Caddy will write logs here.