added demo picture with less JPEG artefacts

README.md

@@ -9,7 +9,7 @@ a searchable list of existing markdown files from CodiMD, i.e., [https://hackmd.
 
 Execute `docker build . --tag codimd; docker run -p 5000:5000 --env TESTING=True codimd` to run the app in testing mode locally. No database credentials are required during testing mode; test data is read from a local file.
 
-### Open issues
+## Open issues
 
 * make the layout responsive
 * either read the DB credentials and URL from the environment or the config file