Fixed: Passing a `MessageProvider` in `Alexa.create` will cause an Exception

A bug fix that resolves the exception that is caused when passing a MessageProvider in Alexa.create.

Initial Release

This is the initial release for alexa_web_api dart package. The features and their description for this release are displayed below.

Features

Alexa Objects - Client

Property	Description	Supported
capabilities	The device capabilities. For details, see Microphone and Capability.	✅
performance	Provides the interface to get the available memory on the device. For details, see Performance.	✅
skill	Provides the interfaces to communicate with your skill. For details, see onMessage and sendMessage.	✅
speech	Provides the interfaces to receive Alexa speech events. For details, see Alexa Speech Input.	✅
version	Version of the Alexa client. If you don't specify a version, the latest version is used.	✅
voice	Provides the interfaces to open the microphone on the device to receive user utterances. For details, see Alexa Voice.	✅

Functions

Property	Description	Supported
create	Establish the connection to Alexa on the device. When the future is completed successful, an AlexaReadyPayload object is returned. Otherwise when the future completes with an error, an ErrorWithCode object is returned. For details, see create.	➖ *

*Even though a MessageProvider can be passed as an parameter in the Alexa.create function, doing this will cause an exception to be thrown.

Fixed Typos in Documentation

The current release fixes typos, and grammatical errors in the read me and documentation files.