Add back button on submissions page

client/src/pages/submissions.vue

@@ -1,5 +1,9 @@
 <template>
   <div class="submissions-page">
+    <div>
+      <a class="button button--primary submissions-page__back" @click="back">Zurück zur Aufgabe</a>
+    </div>
+
     <assignment-with-submissions v-if="!$apollo.queries.assignment.loading"
                                  :assignment="assignment"></assignment-with-submissions>
   </div>
@@ -32,6 +36,12 @@
       },
     },
 
+    methods: {
+      back() {
+        this.$router.go(-1);
+      }
+    },
+
     data() {
       return {
         assignment: {
@@ -46,6 +56,11 @@
   @import "@/styles/_mixins.scss";
 
   .submissions-page {
+    display: grid;
+
+    grid-row-gap: $large-spacing;
+    grid-template-rows: auto 1fr;
+
     @include desktop {
       width: 800px;
     }