Add TypeScript type definitions

[HeyItsBATMAN]

This PR adds TypeScript type definitions, which:

• Cover all public API methods and their parameters
• Include detailed return types for all operations
• Provide proper typing for configuration objects
• Don't change any runtime behavior

Some complex value types are typed as any where the type depends on the property datatype.

I'm open to suggestions on how to further improve this.

Basic examples

[maxlath]

Nice work! I think some of those types or anys could be replaced with types imported from wikibase-sdk, in particular SnakDataValue, which already tries to cover all the datatypes. Do you want to give it a try?

[HeyItsBATMAN]

That makes sense, I'll go and align it with wikibase-sdk then