feat: implement modals with vue router 4

This is an implementation of the modals with the new possibilities of vue router 3.

See: https://github.com/vuejs/vue-router/issues/703#issuecomment-865066913 for a better explanation
and the linked example implementation: https://github.com/vuejs/vue-router-next/blob/master/e2e/modal/index.ts

src/components/tasks/edit-task.vue

@@ -67,7 +67,7 @@
 
 		<router-link
 			class="mt-2 has-text-centered is-block"
-			:to="{name: 'task.detail', params: {id: taskEditTask.id}}"
+			:to="taskDetailRoute"
 		>
 			{{ $t('task.openDetail') }}
 		</router-link>
@@ -102,6 +102,15 @@ export default {
 			taskEditTask: TaskModel,
 		}
 	},
+	computed: {
+		taskDetailRoute() {
+			return {
+				name: 'task.detail',
+				params: { id: this.taskEditTask.id },
+				state: { backgroundView: this.$router.currentRoute.value.fullPath },
+			}
+		},
+	},
 	components: {
 		ColorPicker,
 		Reminders,