added "keep opacity" option, fixed opacity loading, fixed missing shadows not

affecting the preview (i.e. previewing pleroma-dark when redmond is applied)

src/components/style_switcher/style_switcher.vue

@@ -32,6 +32,13 @@
           v-model="keepShadows">
         <label for="keep-shadows">{{$t('settings.style.switcher.keep_shadows')}}</label>
       </span>
+      <span>
+        <input
+          id="keep-opacity"
+          type="checkbox"
+          v-model="keepOpacity">
+        <label for="keep-opacity">{{$t('settings.style.switcher.keep_opacity')}}</label>
+      </span>
       <span>
         <input
           id="keep-roundness"