Update README.md

Author: drizuid

README.md

@@ -158,7 +158,7 @@ Container images are configured using parameters passed at runtime (such as thos
 | `-e APP_URL=` | for specifying the IP:port or URL your application will be accessed on (ie. `http://192.168.1.1:6875` or `https://bookstack.mydomain.com` |
 | `-e DB_HOST=<yourdbhost>` | for specifying the database host |
 | `-e DB_USER=<yourdbuser>` | for specifying the database user |
-| `-e DB_PASS=<yourdbpass>` | for specifying the database password |
+| `-e DB_PASS=<yourdbpass>` | for specifying the database password (non-alphanumeric passwords must be properly escaped.) |
 | `-e DB_DATABASE=bookstackapp` | for specifying the database to be used |
 | `-v /config` | this will store any uploaded data on the docker host |