Type declarations don't match runtime export

[macieklamberski]

Hi there! While wanting to migrate to the new split parser/builder packages, I've noticed inconsistency in the type definitions.

• Types use named export: https://github.com/NaturalIntelligence/fast-xml-builder/blob/main/src/fxb.d.ts#L153-L156
• While the JS uses default: https://github.com/NaturalIntelligence/fast-xml-builder/blob/main/src/fxb.js#L40

This makes it impossible to import correctly - named import type-checks but crashes at runtime, default import works at runtime but fails type-checking.

The fix would be to choose either named or default export and use in both places. Happy to submit a PR for whichever direction you prefer.

[timtucker-dte]

Personal preference here would be for named exports -- that makes transition a drop-in replacement and also accounts for needing to use named imports when importing the type for XmlBuilderOptions

[fredericbahr]

This currently blocks me implementing my desired use-case. If help is needed, im happy to support.