allow keyboard events on shadow root hosts

[mattclough1]

What: Resolves #1153

Why: The current code only allows keyboard entry on elements with a ShadowRoot if the ShadowRoot has a focusable element

How: The getActiveElement function previously checked for the existence of a shadowRoot on the currently active element, since active elements in a shadow DOM make the host element the active element in the light DOM, but this logic ignored the fact that host elements can also be active elements on their own.

Checklist:

• [N/A] Documentation
• [x] Tests
• [x] Ready to be merged

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Sandbox	Source
priceless-thompson-vd5dxf	Issue #1153

[Artur-]

Ran into this same issue today. Can we get a release with it?

[coder-se]

Same here, just ran into this issue. Fantastic that it's already solved. Would love a release with it.