new(Modal): Add topBar and topBarCentered support.

[stefhatcher]

to: @milesj @stefhatcher @hayes @alecklandgraf

Description

new top bar request from design. can put whatever in it! has a border on the bottom with an option to center align (through text-align) the content. works independent of title/subtitle/header.

Motivation and Context

design needs

Testing

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	+0.2%	550.44 KB	549.56 KB	690.06 KB	689.08 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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  },
  "core": {
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    "lib": 706618
  },
  "forms": {
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    "lib": 47577
  },
  "icons": {
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    "lib": 205626
  },
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    "lib": 20770
  },
  "metrics": {
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    "lib": 7729
  },
  "test-utils": {
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    "lib": 5937
  }
}