Add Carbon 3.x support

[cdbeaton]

This package requires Carbon 2.x and cannot be installed when Carbon 3.x is present.

composer require shahmal1yev/blueskysdk:"^1@beta"
./composer.json has been updated
Running composer update shahmal1yev/blueskysdk
Loading composer repositories with package information
Updating dependencies                                 
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Root composer.json requires shahmal1yev/blueskysdk ^1@beta -> satisfiable by shahmal1yev/blueskysdk[v1.4.0-beta1, ..., v1.6.0-beta].
    - shahmal1yev/blueskysdk[v1.4.0-beta1, ..., v1.6.0-beta] require nesbot/carbon 2.x -> found nesbot/carbon[2.0.0, ..., 2.72.6] but the package is fixed to 3.7.0 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command.

Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.

There are a very small number of breaking changes from 2.x to 3.x that probably won't affect this package.

[shahmal1yev]

Sorry, but it's not possible for now. Take a look at this:

https://github.com/CarbonPHP/carbon/blob/ea38ddc60d67d954ba9685ebecae312aa808f42b/composer.json#L43

However, I'll keep it here for future

The funny thing is, I also forgot about the support for 7.4 and even submitted a PR for it :D