fix(core): stop ignoring shadow roots in context

[pomerantsev]

Before: if a shadow root (not the shadow host element, but an actual ShadowRoot instance) is passed as part of context, it's silently ignored.

After: the shadow root node is substituted with its host element for the rest of Axe algorithms to work with.

Closes: #4941

[straker]

Thanks for the pr, it's a great start. For handling shadow roots, instead of adding the host element we should instead add all the children of the shadow root. This way if there are accessibility violations on the host node we do not report them since the shadow root was passed in and not the host node itself.

We'll also want a test added to https://github.com/dequelabs/axe-core/blob/develop/test/core/base/context.js under the describe('include') block that tests that passing a shadow root to the context will add all it's children. You can use createNestedShadowDom (and tests that use it) to make creating the shadow DOM element and children easier.

[CLAassistant]

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[pomerantsev]

Removed by a pre-commit hook.

[pomerantsev]

@straker thanks for the review! I followed your guidance, updated the logic and wrote a test. Could you please take another look?

[pomerantsev]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.You have signed the CLA already but the status is still pending? Let us recheck it.

By the way, I did previously sign the CLA, not sure why the bot is complaining: #4859

[pomerantsev]

Fixed format.