Fix type definition mismatch for emscripten bindings of FontMgr.matchFamilyStyle

[pushpagarwal]

The current type definitions don't match the actual implementation where value objects and emscripten::val types are handled differently by the binding layer. This causes wrong match for typescript client using FontStyle type.

Updated type declarations to correctly reflect the emscripten binding behavior and ensure client written in ts works correctly.

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[pushpagarwal]

JSFiddle showing Problem: https://jsfiddle.net/vxqornfp/

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