HttpOptions::withFiles(array $files) array shape is incorrect

[stetodd]

The array shape for the $files argument to HttpOptions::withFiles(array $files) is defined as array<string, string>, but it should be array<string, UploadedFile>.

There is an existing issue (#97) suggesting strings should be allowed too, in which case it would become array<string, string|UploadedFile>.

[nikophil]

Hi @stetodd

indeed, you're right. Maybe you'd like to provide a PR for this?