Add support for additional headers

[arashnd]

Thanks for incredible gem!!

In our app we want the ability to pass additional headers (We have custom ActiveStorage::Service class inherits from ActiveStorage::Service::AzureBlobService)

There are many use cases where want to send additional headers for example Customer Provided Keys for Encryption

Azure/azure-storage-ruby#221
https://learn.microsoft.com/en-us/azure/storage/blobs/encryption-customer-provided-keys
https://learn.microsoft.com/en-us/rest/api/storageservices/put-blob

Change is fairly simple but I can improve this PR further if necessary.

[JoeDupuis]

This is a good idea. We need to add this for the other endpoints with headers too.
There is a couple more writer methods + the reader methods.
I also want to add some tests.