Async-firebase

* ``messages.Notification`` object now supports attribute ``image`` that allows to set image url of the notification

A few new error types have been added to support the errors that FCM API may return:
- InvalidArgumentError
- FailedPreconditionError
- OutOfRangeError
- UnauthenticatedError
- PermissionDeniedError
- NotFoundError
- AbortedError
- AlreadyExistsError
- ConflictError
- ResourceExhaustedError
- CancelledError
- DataLossError
- UnknownError
- InternalError
- UnavailableError
- DeadlineExceededError

* Adjust type annotations for some errors:

**async_firebase/errors.py**
python

class AsyncFirebaseError(BaseAsyncFirebaseError):
"""A prototype for all AF Errors.

This error and its subtypes and the reason to rise them are consistent with Google's errors,
that may be found in `firebase-admin-python` in `firebase_admin.exceptions module`.
"""

def __init__(
self,
code: str,
message: str,
<<< cause: t.Optional[Exception] = None,
>>> cause: t.Union[httpx.HTTPStatusError, httpx.RequestError, None] = None,
http_response: t.Optional[httpx.Response] = None,
):


**async_firebase/messages.py**
python
class FcmPushResponse:
"""The response received from an individual batched request to the FCM API.

The interface of this object is compatible with SendResponse object of
the Google's firebase-admin-python package.
"""

def __init__(
self,
fcm_response: t.Optional[t.Dict[str, str]] = None,
<<< exception: t.Optional[Exception] = None
>>> exception: t.Optional[AsyncFirebaseError] = None
):

* Fix ``TypeError`` on create ``AsyncFirebaseError`` subclass instance

* `push` method now returns a `FcmPushResponse` object, that has a fully compatible interface with SendResponse object of the Google's firebase-admin-python package.
* `push_multicast` method now returns a `FcmPushMulticastResponse` object, that has a fully compatible interface with BatchResponse object of the Google's firebase-admin-python package.
* The aforementioned methods may still rise exceptions when assembling the message for the request.
* A bunch of exceptions has been added.

* [FIX] Invalid batch requests fixed in``push_multicast`` method.
* [FIX] Data mutation issues that lead to unexpected behaviour fixed in ``assemble_push_notification`` method.
* Message ``messages.MulticastMessage`` was deprecated as it's no longer used.