Add formatting to Slot

plugins/talk-plugin-auth/client/login/components/External.css

@@ -6,3 +6,11 @@
     text-align: center;
     font-size: 1.2em;
 }
+
+.slot > * {
+  margin-bottom: 8px;
+
+  &:last-child {
+    margin-bottom: 0px;
+  }
+}

plugins/talk-plugin-auth/client/login/components/External.js

@@ -9,7 +9,7 @@ const External = ({ slot }) => (
   <IfSlotIsNotEmpty slot={slot}>
     <div>
       <div className={styles.external}>
-        <Slot fill={slot} />
+        <Slot fill={slot} className={styles.slot} />
       </div>
       <div className={styles.separator}>
         <h1>{t('talk-plugin-auth.login.or')}</h1>