feat(cards): support lowercase and capitalized JSON values for Spacing

[cnaples79]

Summary

This PR updates the Spacing type and the JSON schema to support both lowercase and capitalized values for the spacing property in Adaptive Cards. This addresses the inconsistency between the Adaptive Cards Designer, which uses capitalized values, and the linter in this repository, which prefers lowercase values.

Changes

• packages/cards/src/core.ts: Added lowercase and camelCase variants to the Spacing type definition.
• packages/cards/schema.json: Updated the regex for 13.columnSpacing to include ExtraSmall and its variants.

Rationale

This change avoids confusion for developers and improves the developer experience by allowing either casing to be used for the spacing property. Both capitalized and lowercase values are rendered correctly in Teams, so this change makes the SDK more flexible.

Fixes #132

[corinagum]

@cnaples79 thanks for the contribution! Unfortunately this method won't work, since schema.json and core.ts are generated files and would be overwritten next time the schema is updated. I think it would be best to come up with a proposal to handle these programmatically.

IIRC schema.json is not used directly, so core.ts would need to be updated. @aacebo could you verify?

[cnaples79]

@corinagum I see, got it thanks for the feedback. I'll work on updating the implementation.