update readme: clarify no db just text file

readme.md

@@ -1,6 +1,7 @@
 # urls-txt
 
 a _really_ simple url shortener: less than 200 lines of Rust and one dependency (tokio).
+there is no database, just a text file.
 
 ## usage
 
@@ -29,6 +30,8 @@ a _really_ simple url shortener: less than 200 lines of Rust and one dependency
    the default bind address is `127.0.0.0:3000`.
    this can be changed using the environment variable `URLS_TXT_BIND_ADDRESS`.
 
+3. restart to apply changes.
+
 ## usage (docker)
 
 a working [dockerfile](./Dockerfile) and [compose file](./compose.yaml) are provided.