Add <selectedcontent> element

[josepharhar]

The <selectedoption> element is part of the customizable select feature and is being added to HTML here.

It is already implemented in chromium and will be shipped when customizable <select> is shipped.

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labels: needs implementation commitment, needs changelog entry

Closes #0000

test case

• TODO HTML validator
• TODO IBM equal access accessibility checker
• TODO axe-core
• TODO ARC toolkit

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Preview | Diff

[scottaohara]

Noting here that there will need to be an entry for a button as a child of a select as well.

[josepharhar]

Noting here that there will need to be an entry for a button as a child of a select as well.

Where should I put this?

[scottaohara]

Noting here that there will need to be an entry for a button as a child of a select as well.

Where should I put this?

oh no worries @josepharhar that was a note for me, not so much for you.

if you did want to take it on, we'd need a new button as a child of a select entry in the table - using a similar ID like I'm setting up over in html aam el-button-select-child

but really, don't worry about it. i was planning on working on finishing this PR once the HTML/HTML AAM PRs were a bit closer to done.

[scottaohara]

latest commit updates selectedcontent to align with recent HTML AAM changes.

also added in the button as a child of select variant / expectations.