Guzzle 7 support

[reense]

Hello!

First of all: Thank you for your awesome package! 🙂 It really makes using the skyscanner api a breeze.
I'm currently trying to install this package into a Laravel 9 project, which has a hard dependency on Guzzle 7. Therefor, I'm getting the following error whilst installing your package:

  Problem 1
    - Root composer.json requires ozdemirburak/skyscanner-php ^0.2.1 -> satisfiable by ozdemirburak/skyscanner-php[0.2.1].
    - ozdemirburak/skyscanner-php 0.2.1 requires guzzlehttp/guzzle ~6.0 -> found guzzlehttp/guzzle[6.0.0, ..., 6.5.x-dev] but it conflicts with your root composer.json require (^7.2).

Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.
You can also try re-running composer require with an explicit version constraint, e.g. "composer require ozdemirburak/skyscanner-php:*" to figure out if any version is installable, or "composer require ozdemirburak/skyscanner-php:^2.1" if you know which you need.

Are you planning on supporting guzzle 7 in the future?

[ozdemirburak]

Thanks for opening this issue @reense. I'm not sure, but I think this will work with some minor tweaks. I will be happy to check this later if someone does not look for this on Hacktoberfest.