add support for misskey-like cat fields (is cat & speak as cat) and frontend options for this

src/components/settings_modal/tabs/general_tab.js

@@ -135,6 +135,9 @@ const GeneralTab = {
         this.$store.dispatch('setOption', { name: 'postLanguage', value: val })
       }
     },
+    catOptsAvail: {
+      get: function () { return this.$store.getters.mergedConfig.showCatFields }
+    },
     ...SharedComputedObject()
   },
   methods: {