[Feature]: Update package exports to include "Overlay Timer" in default import

[cuberoot]

Code of conduct

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Impacted component(s)

Overlay

Expected behavior

A minor issue, but I came across some of our code that uses the overlay timer directly and it isn't exported from the project.

I would expect to be able to do:

import { OverlayTimer } from '@spectrum-web-components/overlay'

Actual behavior

Right now we are referencing it via src

import { OverlayTimer } from '@spectrum-web-components/overlay/src/overlay-timer.js'

Screenshots

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What browsers are you seeing the problem in?

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How can we reproduce this issue?

1. Go to '...'
2. Click on '....'
3. Scroll to '....'
4. Check console
5. See error

Sample code that illustrates the problem

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Logs taken while reproducing problem

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