Implement support for Highlight annotations

Fixes #5018.

Highlight annotations are basically nothing more than the already implemented Text annotations. Therefore a Highlight annotation can be represented as a Text annotation according to the PDF specification at https://www.adobe.com/content/dam/Adobe/en/devnet/acrobat/pdfs/pdf_reference_1-7.pdf#page=633&zoom=auto,-306,268.

Note that for the issue mentioned in this PR the annotations itself are fixed with this PR, but the annotation content is rotated. This is a separate issue (due to the transform on `annotText` that also affects child elements such as the annotation content) and I think it also related to #3826. This should be filed as a follow-up issue.