v4.0.0

Refactoring + Laravel 9 support

• Fix CI pipeline (was using outdated Ubuntu 16)
• No need for our own config/monolog-kinesis.php file, we can piggy back on config/services.php for default AWS creds
• Using the decorator pattern to create src/Kinesis.php in order to avoid binding the raw KinesisClient from the AWS SDK into the container. Let's say we need this Client to stream another kind of data through Kinesis but using another region or another set of credentials, we wouldn't be able to resolve a different instance, with a different config. This gives us much more control over our Client and makes it easier to test too.
• Binding against an interface instead of a class so it's easier to test and makes it bespoke to our package as we're binding against PodPoint\MonologKinesis\Contracts\Client instead of Aws\Kinesis\KinesisClient.
• Ability to define AWS creds both at channel level and at config/services.php level (for the defaults)
• Add missing tests
• Improve naming convention
• Update README.md
• Automatically update CHANGELOG.md upon new releases
• Adding Laravel 9 and PHP 8.1 support