feat: AzureAD provider

[wp-ericdudley]

This PR adds AzureAD as a Single Sign-On (SSO) provider the plugin, allowing users to authenticate using their AzureAD application registrations. The implementation follows the same shape as the current providers.

Key features:

• AzureAD OAuth2 client ID and secret configuration
• Tenant ID configuration
• Callback URL and scope configuration
• Updated documentation for AzureAD integration

Testing:

• I verified that this implementation worked for my company's AzureAD tenant + application.
• Please follow the updated documentation to set up AzureAD integration and ensure that users can successfully authenticate using their AzureAD credentials.

[wp-ericdudley]

@yasudacloud Added this for my company, thought I'd see if you were open to adding more integrations to this package.

[yasudacloud]

@wp-ericdudley Thanks for the PR. There is nothing wrong with adding a provider. I would like to use Azure to check the operation and would appreciate a few days of your time.

[yasudacloud]

@wp-ericdudley Thanks for the PR. I will merge this fix and release it to npm tomorrow in version 0.2.0 after final confirmation that it works.