Use submit event for add column button

src/components/AddColumn/PublicTimeline.vue

@@ -1,13 +1,15 @@
 <template>
   <div>
     <div v-if="showInput">
+      <form @submit.prevent="addTL">
         <input type="text" placeholder="e.g:mstdn.jp" v-model="instance">
         <BaseButton
-        @click.native="addTL"
+          type="submit"
           class="primary fill"
           style="--font-size:.8em;"
           :disabled="!hasDomain"
         >Add Column</BaseButton>
+      </form>
     </div>
     <div id="timelines">
       <div v-for="(value, key, index) in pubTL" :key="index" class="tl">