Add a dev mode to facilitate debugging

www/common/sframe-common-outer.js

@@ -302,6 +302,7 @@ define([
                         password: password,
                         channel: secret.channel,
                         enableSF: localStorage.CryptPad_SF === "1", // TODO to remove when enabled by default
+                        devMode: localStorage.CryptPad_dev === "1",
                     };
                     if (window.CryptPad_newSharedFolder) {
                         additionalPriv.newSharedFolder = window.CryptPad_newSharedFolder;