[Documentation]: Highlight API changes

[jonniebigodes]

Describe the problem

Related to #30894

The upcoming release will restructure the Highlight module and change the API. Therefore, the documentation should be updated accordingly to reflect the changes.

What needs to happen:

• Update the documentation to reflect the changes in the Highlight module
• Remove any examples or references to the old API
• Add examples for the new API
• Adjust the migration guide to reflect the changes in the Highlight module

Additional context

No response

[kylegach]

I think this was handled in #31148.

[jonniebigodes]

Per @ghengeveld's pr and comment, the API changed a bit. Hence, I created it and am going to re-open it and leave it assigned to me. I want to test it out once it's added to the alpha/beta (wherever this lands).

[ghengeveld]

That's right, the highlights API has (significantly) changed since @jonniebigodes' previous PR. That one was mostly about it becoming a core module instead of an addon. The work done in #30894 is much more elaborate. The PR description contains details about the new API.