Add Support for Anchor Links

[kevinfodness]

Description

Apple News supports anchor links (e.g., #my-cool-heading) but this plugin does not. It intentionally converts various types of referential links to absolute URLs so that they don't break when sent to Apple News (e.g., a relative link like /my-example-page would be rewritten to include the domain, like https://www.example.org/my-example-page). It would be good to remove this behavior for anchor links and instead make anchor links work properly. In order to do that, we will need to add an identifier property to components based on the id of the HTML element.

ref: https://developer.apple.com/documentation/apple_news/apple_news_format/components/using_html_with_apple_news_format

Use Case

As an editor, I want to be able to create anchor links within my document that work on Apple News as well as natively on my site.

Acceptance Criteria

• Remove the logic that adds the permalink to the anchor link, leaving the anchor link intact.
• Add parsing for IDs and add IDs as identifiers to components so that they can be accessed by anchor links. Use the first (top-level) ID found within component HTML as the identifier for the component.