update(Modal): Add optional zIndex to props

[nilgradisnik]

to: @williaster @alecklandgraf

Description

Allow for optional zIndex to be passed to Modal.

Motivation and Context

We want to override z-index for Modals that are in a Lighbox component where a recent change increased the z-index https://github.com/airbnb/lunar/pull/411. This allows to bring such Modals to the front.

Testing

Tested in storybook

Screenshots

Checklist

• My code follows the style guide of this project.
• I have updated or added documentation accordingly.
• I have read the CONTRIBUTING document.

[airbnb-bot]

Size Changes

Package	Diff	ESM	Prev ESM	CJS	Prev CJS
core	+0.0%	570.87 KB	570.69 KB	715.98 KB	715.76 KB

Compared to master. File sizes are unminified and ungzipped.

View raw build stats

Previous (master)

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Current

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  },
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  },
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  },
  "core": {
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    "lib": 733164
  },
  "forms": {
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    "lib": 49298
  },
  "icons": {
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  },
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    "lib": 20770
  },
  "metrics": {
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    "lib": 7729
  },
  "test-utils": {
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    "lib": 5937
  }
}