Implement getHeaders method in Curl class

[mean-cj]

Add method to retrieve custom headers in Curl class.

[nadar]

@mean-cj what about using this method to retrieve response headers?

 /**
     * Get a specific response header key or all values from the response headers array.
     *
     * Usage example:
     *
     * ```php
     * $curl = (new Curl())->get('http://example.com');
     *
     * echo $curl->getResponseHeaders('Content-Type');
     * ```
     *
     * Or in order to dump all keys with the given values use:
     *
     * ```php
     * $curl = (new Curl())->get('http://example.com');
     *
     * var_dump($curl->getResponseHeaders());
     * ```
     *
     * @param string $headerKey Optional key to get from the array.
     * @return bool|string|array
     * @since 1.9
     */

[mean-cj]

Hi @nadar,

Hope you are doing well : )

I added the getHeaders() function to allow retrieving the HTTP headers that were previously added using the setHeaders() function.

These values represent the HTTP request headers that will be sent through the cURL request.

The returned values are only the request headers and are not mixed with the ResponseHeader.

Thanks.