[Feature]: react-message-bar: Allow custom style on bottomReflowSpacer slot

[soumyart]

Area

React Components (@fluentui/react-components)

Describe the feature that you would like added

Support custom style on bottomReflowSpacer slot.

Additional context

In useMessageBarStyles.styles.ts external className is not allowed on bottomReflowSpacer slot .

I can create a PR for this enhancement if FluentUI team approves this as a valid feature.

Have you discussed this feature with our team

No response

Validations

• Check that there isn't already an issue that requests the same feature to avoid creating a duplicate.

Priority

Medium