Handle multiple-valued query parameters in queryParams

[Hendy Irawan]

Currently queryParams assumes that queryParams is a Record, meaning it's not possible to have, e.g.

https://example.com/?branch=valueA&branch=valueB

Note: URLSearchParams already supports multiple valued query parameters (appending parameters with the same name).

This should be fixed to allow multiple values.

[Ruslan]

@ceefour please take a look, #218
You can copy this to your *Fetcher.ts file

[Fabien BERNARD]

As mentionned in your pull-request, {namespace}Fetcher.ts is a template copied once, so you can tweak it as much as you want to fit your usecase 😉