Create Check interface class

[mehulkaklotar]

The Check interface will be implemented by all concrete check classes. Using an interface helps to define required methods for checks and enforce those on concrete check classes. This ensures that these methods are available to use by other structures in the plugin reliably. Currently, the interface will likely define a single run method but this may be expanded on in the future.

Acceptance Criteria

• A new Check interface class is created
• The Check interface contains a single public run() method
• The run method accepts a single $result parameter
• The $result parameter is an instance of the Check_Result class
• Full method - public function run( Check_Result $result )
• If the Check_Result class does not exist in the repo, create an empty Check_Result class as a scaffold to be implemented in Create Check_Result class #11