💄(frontend) Title header optional

On the DSFR instance the title will not
be displayed anymore in favor of
a icon that include the title.
So we make the title optional, it
will be configurable from the
theme configuration.

src/backend/impress/configuration/theme/default.json

@@ -145,7 +145,8 @@
         "width": "32px",
         "height": "auto"
       },
-      "alt": ""
+      "alt": "",
+      "withTitle": true
     }
   },
   "favicon": {