JSX inside of code blocks is rendered in docs

[lucacasonato]

/**
 * ```tsx
 * export default definePage<typeof handler>(({ data }) => {
 *   return <h1>{data.message}</h1>;
 * });
 * ```
 */
export function foo() {}

Results in something like this in the docs:

This is with deno doc --html on Deno 1.42.1

[crowlKats]

Closing as fixed in #554