Add Laravel 9.x support

[mdasifiqbal]

Can you please add support for Laravel 9? I reckon the change would be similar to this PR - #99

Currently I'm getting following error while using Laravel 9 and PHP 8 -

    - illuminate/support[v5.6.0, ..., 5.8.x-dev] require php ^7.1.3 -> your php version (8.0.18) does not satisfy that requirement.
    - illuminate/support[v6.0.0, ..., v6.19.1] require php ^7.2 -> your php version (8.0.18) does not satisfy that requirement.
    - illuminate/support[v7.0.0, ..., v7.28.4] require php ^7.2.5 -> your php version (8.0.18) does not satisfy that requirement.
    - illuminate/support[v8.0.0, ..., v8.11.2] require php ^7.3 -> your php version (8.0.18) does not satisfy that requirement.
- superbalist/laravel-google-cloud-storage 2.2.4 requires illuminate/support ^5.1|^6.0|^7.0|^8.0 -> satisfiable by illuminate/support[v5.1.1, ..., 5.8.x-dev, v6.0.0, ..., 6.x-dev, v7.0.0, ..., 7.x-dev, v8.0.0, ..., 8.x-dev].
    - superbalist/laravel-google-cloud-storage 2.2.3 requires illuminate/support ^5.1|^6.0|^7.0 -> satisfiable by illuminate/support[v5.1.1, ..., 5.8.x-dev, v6.0.0, ..., 6.x-dev, v7.0.0, ..., 7.x-dev].
    - superbalist/laravel-google-cloud-storage 2.2.2 requires illuminate/support ^5.1|^6.0 -> satisfiable by illuminate/support[v5.1.1, ..., 5.8.x-dev, v6.0.0, ..., 6.x-dev].
    - superbalist/laravel-google-cloud-storage[2.2.0, ..., 2.2.1] require illuminate/support ^5.1|^5.2|^5.3 -> satisfiable by illuminate/support[v5.1.1, ..., 5.8.x-dev].
    - Only one of these can be installed: illuminate/support[v5.1.1, ..., 5.8.x-dev, v6.0.0, ..., 6.x-dev, v7.0.0, ..., 7.x-dev, v8.0.0, ..., 8.x-dev, v9.0.0-beta.1, ..., 9.x-dev], laravel/framework[v9.0.0-beta.1, ..., 9.x-dev]. laravel/framework replaces illuminate/support and thus cannot coexist with it.

[mdasifiqbal]

Duplicate of #118