fix: downstream type inference for Float/Int schemas

[jacob-alford]

This is necessary because of an issue with type-inference for downstream buildable libraries which emit .dts. Without exporting these brands, TypeScript can't know what the underlying types are. This became an issue introducing the type alias for float / int default values. Changing that to an interface also fixes the issue, but Opaque from type-fest is a type-alias and hence cannot be upstream to an interface.

[coveralls]

Pull Request Test Coverage Report for Build 7036745337

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 6805819319:	0.0%
Covered Lines:	2597
Relevant Lines:	2597

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💛 - Coveralls