Add support for query strings that contain duplicate keys

[aran112000]

Currently when a query string is parsed, PHP's parse_str() will remove any duplicate keys and will only preserve the final value.

Example

?key=value1&key=value2 = key: "value2"

Expected value

?key=value1&key=value2 = key: ["value1", "value2"]

This PR normalises these formats before processing so these strings will become array notation which is then correctly parsed by PHP's parse_str().

[otsch]

Already added it to the changelog, but to also make it visible here:

This is considered a bugfix because:

• Previously foo=bar&foo=baz became foo=baz, which is most likely unwanted behavior.
• Of course, such query strings should preferably be written using the array notation ([]), but if such a query is written without the brackets, the intention is either that it should be an array, or it's a mistake. If it is a mistake, the probability to notice it is higher, when the result contains all values instead of only the last one.
• As this library is also part of the crwlr crawling library and there are servers intentionally using the syntax without brackets (e.g. google https://fonts.googleapis.com/css2?family=Baloo&family=Roboto) it's better to interpret it as an array.

[aran112000]

Amazing, thanks for your support and quick turnaround on this @otsch

[otsch]

Of course. Thank you for the contribution @aran112000 ! 🙏🏻🙂👏🏻