Ignore Enter key when converting text (for Japanese characters)

See vuejs/vuepress#2851

components/SearchBox.vue

@@ -1,5 +1,6 @@
 <template>
   <div class="search-box">
+    <form @submit.prevent="go(focusIndex)">
     <input
       ref="input"
       aria-label="Search"
@@ -11,10 +12,10 @@
       @input="query = $event.target.value"
       @focus="focused = true"
       @blur="focused = false"
-      @keyup.enter="go(focusIndex)"
       @keyup.up="onUp"
       @keyup.down="onDown"
     />
+    </form>
     <ul v-if="showSuggestions" class="suggestions" :class="{ 'align-right': alignRight }" @mouseleave="unfocus">
       <li
         v-for="(s, i) in suggestions"