added about on consistency

public/index.html

@@ -966,6 +966,8 @@ <h1>stats</h1>
           <p>raw wpm - calculated just like wpm, but also includes incorrect words.</p>
           <p>acc - percentage of correctly pressed keys.</p>
           <p>char - correct characters / incorrect characters. Calculated after the test has ended.</p>
+          <p>consistency - based on the variance of your raw wpm. Closer to 100% is better. Calculated using the
+            coefficient of variation of raw wpm and mapped onto a scale from 0 to 100.</p>
         </div>
         <div class="section">
           <h1>results screen</h1>