Malformed HTML when <a/> tag is already present

Problem/Motivation

Currently the photoswipe logic just loops over all elements in the DOM which are an img node. If a content editor in the CKEditor already added a link around the image (a tag) you end up with an A tag in an A tag which is malformed HTML. The browser will try to correct this by putting the first A tag above the other elements, but this results in the content editors link not working.

The end game would be #3546923: Make the swiper toggle-able in CKEditor, but I think this is a great in between step.

Steps to reproduce

In a photoswipe enabled CKEditor, upload an image and add in the ckeditor a link to https://google.com. Observe the rendered HTML.

Proposed resolution

Check all parents if there is an A tag already around the DOM element. If present we skip the photo swipe logic.

Remaining tasks

MR

User interface changes

N/A

API changes

N/A

Data model changes

N/A