Chore/vonage video shim

[SecondeJK]

This PR provides a shim layer to divert traffic to the Vonage Video API with a JWT created from the application id and private key from the Vonage Video Dashboard.

Description

You can now add these options in, and the SDK will take care of the rest.

use OpenTok\OpenTok;
use MyCompany\CustomOpenTokClient;

$options = [
    'application_id' => 'your_application_id',
    'private_key_path' => './path-to-your.key'
]

$opentok = new OpenTok($apiKey, $apiSecret, $options);

Motivation and Context

Backwards compatibility shim while developers shift to the new platform.

How Has This Been Tested?

Test added to cover the scenario

Example Output or Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.