[DomCrawler] Added support for <area> tags to be treated as links

The [HTML area tag](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/area) behaves exactly like the `a` tag in that they're both clickable, and if it has a `href` follows a link. The Link class works the same with both tags.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |