more FA5 stuff with small related refactoring

src/components/panel_loading/panel_loading.vue

@@ -1,12 +1,21 @@
 <template>
   <div class="panel-loading">
     <span class="loading-text">
-      <i class="icon-spin4 animate-spin" />
+      <FAIcon icon="circle-notch" spin size="3x"/>
       {{ $t('general.loading') }}
     </span>
   </div>
 </template>
 
+<script>
+import { library } from '@fortawesome/fontawesome-svg-core'
+import { faCircleNotch } from '@fortawesome/free-solid-svg-icons'
+
+library.add(
+  faCircleNotch
+)
+</script>
+
 <style lang="scss">
 @import 'src/_variables.scss';
 
@@ -18,8 +27,7 @@
   font-size: 2em;
   color: $fallback--text;
   color: var(--text, $fallback--text);
-  .loading-text i {
-    font-size: 3em;
+  .loading-text svg {
     line-height: 0;
     vertical-align: middle;
     color: $fallback--text;