Improve WebAPI compatibility

[g105b]

https://developer.mozilla.org/en-US/docs/Web/API

There are a few classes in the WebAPI that have functionality shared by this implementation of PSR-7 which should be implemented.

Functions:

• Message::arrayBuffer() - Returns a promise
• Message::blob() - Returns a promise
• Message::formData() - Returns a promise
• Message::json() - Returns a promise
• Message::text() - Returns a promise

Properties:

• Response::ok
• Response::headers
• Response::redirected
• Response::status
• Response::statusText
• Response::type
• Response::uri
• Response::useFinalUri

---

• Request::cache
• Request::context
• Request::credentials
• Request::destination
• Request::headers
• Request::integrity
• Request::method
• Request::mode
• Request::redirect
• Request::referrer
• Request::referrerPolicy
• Request::url

---

• The Headers class needs to have its methods made compatible (https://developer.mozilla.org/en-US/docs/Web/API/Headers).

• The FormData class needs fully implementing.

• The Stream class should be broken down into ReadableStream and WritableStream.

[g105b]

Before any of this can be completed, the Promise class needs to be available from https://github.com/PhpGt/Async

[g105b]

FormData class was left as a stub in the repository which is now failing PHPStan. Here's the class:

<?php
namespace Gt\Http;

class FormData {
	/** @var array */
	protected $data;

	public function __construct(array $data = []) {
		$this->data = $data;
	}

	public function append(
		string $key,
		string $value,
		string $filename = null
	):void {

	}

	public function set(
		string $name,
		string $value,
		string $filename = null
	):void {

	}

	public function delete(string $name):void {

	}

	public function entries():array {

	}

	public function get(string $name):?string {

	}

	public function getAll(string $name):array {

	}

	/** For consistency with naming of other Web APIs. */
	public function contains(string $name):bool {

	}

	public function has(string $name):bool {

	}

	public function keys():array {

	}

	public function values():array {

	}
}

[g105b]

Different Body types that need implementing:

body
Any body that you want to add to your request: this can be a Blob, BufferSource, FormData, URLSearchParams, USVString, or ReadableStream object. Note that a request using the GET or HEAD method cannot have a body.

[g105b]

This latest push has implementations of some of the classes, and properties have been made consistent.

Still to do:

1. Complete the class implementations.
2. Link the external async loop to the promises.