title: How to validate non required filed in Yup
body: <p>How to validate a non required filed that should not contain the following special characters  <code>#&lt;`&gt;</code> and a white space before dot(.) I have Regex <code>\`|\#|\&amp;|\&lt;|\ \.|\&gt;</code> to validate above condition but don't have any idea how to this regex with the yup.matches(). Thanks in advance </p>
  
  <pre><code>Regex: \`|\#|\&amp;|\&lt;|\ \.|\&gt; 
  </code></pre>
  
  <p>my validation schema is:</p>
  
  <pre><code>const validationSchema = function (values) {
    var regx = new RegExp(/\`|\#|\&amp;|\&lt;|\ \.|\&gt;/gms);
      return Yup.object().shape({
        about: Yup.string()
        .matches(expression, 'about should not contain ` # &lt; &gt; \n')
  
      })
    }
  </code></pre>