better separation + style of PWA manifest

src/components/settings_modal/admin_tabs/instance_tab.vue

@@ -57,6 +57,7 @@
         <li>
           <GroupSetting path=":pleroma.:manifest" />
         </li>
+        <h4>{{ $t('admin_dash.instance.misc_brand') }}</H4>
         <li>
           <AttachmentSetting path=":pleroma.:instance.:background_image" />
         </li>

src/components/settings_modal/helpers/pwa_manifest_icons_setting.vue

@@ -137,6 +137,8 @@
 <script src="./pwa_manifest_icons_setting.js"></script>
 <style lang="scss">
 div.PWAManifestIconsSetting {
+  margin-left: 3em;
+
   &.setting-item {
     display: grid;
     grid-template-areas: