Feature: Render Heading anchors like on GitHub and NPMjs

[bradleyburgess]

If you create a README in a GitHub repo or your NPM package, anchors are automatically generated from your headings. This allows you to create a TOC which links to the various sections in your readme.

E.g.:

# My Heading

Lorem ipsum...

will result in this HTML:

<h1 id="my-heading">My Heading</h1>
<p>Lorem ipsum...</p>

Unfortunately, TOC links on npmtrends.com are broken.