allow InputProps and OutputProps to be typed in generated Load

[ivanhofer]

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Same fix as here: #4160
But this time for the generated Load type.

I also have restricted all the Params and Props types with the extends keyword.
Maybe it makes sense to create a "base type" and use it everywhere:

+type BaseParams = Record<string, string> +type BaseProps = Record<string, any> export interface Load< -Params extends Record<string, string> = Record<string, string>, -InputProps extends Record<string, any> = Record<string, any>, -OutputProps extends Record<string, any> = InputProps +Params extends BaseParams = BaseParams, +InputProps extends BaseProps = BaseProps, +OutputProps extends BaseProps = InputProps > {	(input: LoadInput<Params, InputProps>): MaybePromise<	Either<Fallthrough, LoadOutput<OutputProps>>	>; } 

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Latest commit: 2d367e7

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[ivanhofer]

I also have noticed the same issue with the generated RequestHandler type.
It was already included in the docs but the generated type was wrong. I included the fix in this PR.

I'm not sure what to do with the Body type from the "private" types. Can I move it to index.d.ts?

[Rich-Harris]

Thanks! Yeah, it makes sense to expose Body. I've updated this PR so that it's exposed as ResponseBody