title: Vue 3: Is getCurrentInstance() deprecated?
body: <p>I've seen references to <code>getCurrentInstance()</code> function on some old(?) documents and codes, but cannot find it in the current Vue 3 document.</p>
  <p>Is <code>getCurrentInstance()</code> deprecated?</p>
  <p>If so, what is the reason? (<code>inject()</code> considered enough?) If not, why can't I find it in the document?</p>