Re: [dom] Added an example showing feature detection with supports() (#144)

> @@ -8705,6 +8705,28 @@ associated <a for="/">element</a>'s
>    <p>Throws a <code>TypeError</code> exception if the associated attribute has no supported tokens defined.
>  </dl>
>  
> +<p>The <a method for=DOMTokenList lt="supports()">supports()</a> method can be used to detect support for {{DOMTokenList}} tokens:
> +<pre class=lang-javascript>
> +var DOMTokenListSupports = function(tokenList, token) {
> +      if (!tokenList || !tokenList.supports) {
> +          return false;
> +      }
> +      try {
> +          return tokenList.supports(token);
> +      } catch (e) {
> +          if (e instanceof TypeError) {
> +            console.log("The DOMTokenList doesn't have a supported tokens list");
> +          } else {
> +            console.error("That shouldn't have happened");
> +          }

Also, `console` is not standardized. I guess that doesn't matter.

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