link til underartikkel som router-link

src/components/SubArticle.vue

 <template>
   <li class="sub_article">
-    <span class="sub_article_header"><a :href="body.article_id">{{body.lemmas[0]}}</a></span>
+    <span class="sub_article_header">
+      <router-link :to="body.article_id"  @click.native="article_link_click(body)">
+        {{body.lemmas[0]}}
+      </router-link>
+    </span>
     <ul>
       <DefElement :body="body.intro" v-if="body.intro" @article-click="article_link_click" />
       <Definition :body="body.article.body.definitions[0]" @article-click="article_link_click" />