support target in header links

src/components/shared/header-link.vue

@@ -26,9 +26,11 @@ li.header-entry
   a(
     v-else-if='!sameSite'
     :href='entry.path'
+    :target='entry.target || "_self"'
   ) {{ entry.displayName }}
   router-link(
     v-else
     :to='{ name }'
+    :target='entry.target || "_self"'
   ) {{ entry.displayName }}
 </template>

src/content-env.d.ts

@@ -100,6 +100,12 @@ declare module 'content/routes.js' {
     displayName: string
   } & ({
     path: string
+    target?:
+      | '_self'
+      | '_blank'
+      | '_parent'
+      | '_top'
+      | '_unfencedTop'
   } | {
     children: HeaderEntry[]
   })