Support AAD authentication

[ADRDev]

Could support be added for AAD authentication method as mentioned in the azure storage php repo? https://github.com/Azure/azure-storage-php/

It appears very similar to SAS method but passing account name instead of saskey.

[matthewbdaly]

I don't see any reason why not, but I think the critical thing is probably whether it's possible to do it with Flysystem's Azure driver, since this package is just a wrapper for that so it can be used with the Laravel storage API.

I don't have the bandwidth to work on it, but I'd be happy to consider any pull request.