Add a slot to Overlay for a filter

[jonrohan]

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What are you trying to accomplish?

I need to add slot in Overlay::Header that will allow me to put a filter input below the title and close button.

The Overlay::Header will already render content if provided, however this won't be useful because it replaces the title in this grid which becomes too much of a hack to try and override to get it away from the close button:

Screenshots

Integration

No

List the issues that this change affects.

Needed for https://github.com/github/github/pull/316178

Risk Assessment

• Low risk the change is small, highly observable, and easily rolled back.
• Medium risk changes that are isolated, reduced in scope or could impact few users. The change will not impact library availability.
• High risk changes are those that could impact customers and SLOs, low or no test coverage, low observability, or slow to rollback.

[changeset-bot]

🦋 Changeset detected

Latest commit: 78591b1

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

This PR includes changesets to release 1 package

Name	Type
@primer/view-components	Minor

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