Support Duplicate Query String Keys

[evanlemke]

/my-page?foo=bar&foo=bar results in an error caused by calling Object.assign(obj[key], val) on an existing string

Uncaught TypeError: Cannot assign to read only property '0' of object '[object String]'

According to RFC 3986, which defines the URI (Uniform Resource Identifier) syntax, the query component can include duplicate keys. Instead of erroring, ignore duplicates.

The query component is defined as a string of characters beginning with a ? and consisting of a series of key=value pairs, each of which is separated by an &. In the case where multiple pairs with the same key exist, the behavior is application-specific, and it's up to the server or client to define how they handle such cases.

[evanlemke]

@PaulMaly bump