Allow the query option to be a URLSearchParams instance

[lorenzofox3]

Fixes #554

[sindresorhus]

@lorenzofox3 This causes a test failure.

[lorenzofox3]

@sindresorhus
I think the test is failing is because the URLSearchParams implements properly the standard url encoder parser and serializer which means ?foo is correctly parsed and serialized to ?foo= (which dose not match the redirect url ?foo of the test server). I see then different solutions.

1. Modify the test and consider ?foo is equivalent ?foo= on the test server side (which is the case according to the spec aforementioned if I understand correctly)
2. Change the implementation to have our own toString so that empty values are ignored and the = sign is not appended. However this could lead to inconsistent behavior.
   query parameters with following parameters may not output the same queryString:
   ?foo
?foo=''
?foo=''
{query:undefined}
{query:''}

On a side note: I am not sure whether it is a problem with the test framework or the reporter but when running the tests I man not able to say it is actually failing: when I run the tests the final output is

[szmarczak]

@lorenzofox3 is right.

This:

got/test/redirects.js

Line 85 in 8f30f1f

http.on('/relativeQuery?bang', (request, response) => {

should be

 http.on('/relativeQuery?bang=', (request, response) => { 

and the tests would pass. I think we should use lukeed/polka because it's very lightweight and blazing fast. I highly recommend it :)