Capture element selections through useSelected

[samarsault]

Description
Element selections were not captured by the useSelected hook

Issue
Fixes: #4338

Example (Before)

Borrowed from #4338.
Code - https://jsfiddle.net/4c21gd5v/22/

Example (After)

Context
From the code, It seems like the Element does not have access to the SelectedContext, but all elements inside it do. So instead of inside the Element, I wrapped the SelectionContext around the element as following:

<SelectedContext.Provider value={!!sel}>
  <ElementComponent
      ...
  />
</SelectedContext.Provider>

Checks

• The new code matches the existing patterns and styles.
• The tests pass with yarn test.
• The linter passes with yarn lint. (Fix errors with yarn fix.)
• The relevant examples still work. (Run examples with yarn start.)
• You've added a changeset if changing functionality. (Add one with yarn changeset add.)

[changeset-bot]

🦋 Changeset detected

Latest commit: 7ae7bd5

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
slate-react	Patch

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[cboppert]

Looks good to me, will leave up to @BrentFarese or @timbuckley for a final approval

[dylans]

Apologies @samarsault , there's a merge conflict from a PR we landed yesterday. Could you please rebase when you have a moment. Also if you could create a changeset (see the comment in the PR) then I'll go ahead and merge into main. Thanks!