[enhancement] Set minimum version to illuminate/support": "^8

[jwambugu]

The package currently requires "illuminate/support": "^5.0|^6.0|^7.0|^8.0" which pulls in versions ^5.0|^6.0|^7.0 which might not be getting any security fixes.

Can we have another version which will require the minimum version of illuminate/support to be ^8. This will ensure new projects or updates which satisfy this requirement will also get the security fixes.

[gathuku]

@jwambugu The only support component am using is File::get
Maybe rewriting this to get rid of the File support component can be the best. How do you think?
https://github.com/gathuku/laravel_mpesa/blob/master/src/Mpesa.php#L137-L146

[jwambugu]

The whole support package provided a lot of functionality which we can extend to use and refactor this package. And since it's a laravel package, I feel it should remain. That's my opinion 😁