title: confusion about `useSelector` and `createSelector` with Redux toolkit
body: <p>I am new to Redux and Redux toolkit. I learned that <code>createSelector</code> can accept multiple input selectors, which can be provided as separate arguments or as an array. The results from all the input selectors are provided as separate arguments to the output selector.</p>
  <pre class="lang-js prettyprint-override"><code>const selectA = state =&gt; state.a;
  const selectB = state =&gt; state.b;
  const selectC = state =&gt; state.c;
  
  const selectABC = createSelector(
      [selectA, selectB, selectC],
      (a, b, c) =&gt; {
          // do something with a, b, and c, and return a result
          return a + b + c;
      }
  );
  </code></pre>
  <p>my question is, if I only care about one simple state, can I just use <code>useSelector</code> like this</p>
  <pre class="lang-js prettyprint-override"><code>const selectA = state =&gt; state.a;
  
  const a = useSelector(selectA)
  </code></pre>
  <p>what's the difference between the two usages?</p>