feat(theme): allow internal social links

closes #5305

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

@@ -1,7 +1,7 @@
 <script lang="ts" setup>
 import type { DefaultTheme } from 'vitepress/theme'
 import { computed, nextTick, onMounted, ref, useSSRContext } from 'vue'
-import type { SSGContext } from '../../shared'
+import { isExternal, type SSGContext } from '../../shared'
 
 const props = defineProps<{
   icon: DefaultTheme.SocialLinkIcon
@@ -46,7 +46,7 @@ if (import.meta.env.SSR) {
     class="VPSocialLink no-icon"
     :href="link"
     :aria-label="ariaLabel ?? (typeof icon === 'string' ? icon : '')"
-    :target="target ?? '_blank'"
+    :target="target ?? (isExternal(link) ? '_blank' : undefined)"
     :rel="me ? 'me noopener' : 'noopener'"
     v-html="svg"
   ></a>