README.md: added extra info

README.md

@@ -21,6 +21,12 @@ source venv/bin/activate
 python -m pip3 install -r requirements.txt
 ```
 
+Create a configuration file (and set the secret key!)
+```
+cp config.yml.example config.yml
+vim config.yml
+```
+
 Start Flask in development mode:
 
 ```
@@ -42,3 +48,17 @@ Please use the linter before submitting code.
 ```
 black .
 ```
+
+## database maintenance
+
+To clean up the database (remove stale entries):
+
+```
+flask --app sachet.server cleanup
+```
+
+Otherwise, to upgrade the database after a schema change:
+
+```
+flask --app sachet.server db upgrade
+```