feat: add "Documentation" link to "About" page (#2734)

locales/en.json

@@ -306,6 +306,7 @@
     "built_at": "Built {0}",
     "compose": "Compose",
     "conversations": "Conversations",
+    "docs": "Documentation",
     "explore": "Explore",
     "favourites": "Favorites",
     "federated": "Federated",

pages/settings/about/index.vue

@@ -58,6 +58,13 @@ function handleShowCommit() {
       @click="openPreviewHelp"
     />
 
+    <SettingsItem
+      :text="$t('nav.docs')"
+      icon="i-ri:book-open-line"
+      to="https://docs.elk.zone/"
+      large target="_blank"
+    />
+
     <SettingsItem
       text="Mastodon"
       icon="i-ri:mastodon-line"