fix(theme): external link icon not visible for target _blank links

closes #3327

src/client/theme-default/components/VPLink.vue

@@ -12,7 +12,11 @@ const props = defineProps<{
 }>()
 
 const tag = computed(() => props.tag ?? (props.href ? 'a' : 'span'))
-const isExternal = computed(() => props.href && EXTERNAL_URL_RE.test(props.href))
+const isExternal = computed(
+  () =>
+    (props.href && EXTERNAL_URL_RE.test(props.href)) ||
+    props.target === '_blank'
+)
 </script>
 
 <template>