This commit uses the Jekyll `link` tag to correctly construct the URL to
images with otherwise relative paths. Without this logic, the images
would only load when the landing page's permalink was not altered by the
user. For example, if the permalink is changed to `get-started` in the
Jekyll Front Matter, the relative URLs would become:

    get-started/assets/images/pic08.jpg

However, since the `get-started` path doesn't really exist, this would
fail to load the image.

As of Jekyll 4.0, the `link` tag is safe to use without prepending
`site.baseurl`, so this code works in all situations.