docs (#170): improve phrasing

Author: bencodezen

src/.vuepress/components/BetaBanner.vue

@@ -4,7 +4,10 @@ export default {}
 
 <template>
   <aside class="beta-banner">
-    <p>⚠️ Beta Version: Docs are still under development and may change. ⚠️</p>
+    <p>
+      ⚠️ Beta Version: Docs are still under development and are subject to
+      change. ⚠️
+    </p>
   </aside>
 </template>