[Speech] Sample for building custom microphone input

[compulim]

Related to #3974.

Feature Request

We introduced packages/bundle/src/speech/createAudioConfig.ts in #3974. It can be used to implement microphone input for Speech SDK, outside of Web Audio API.

Web devs on React Native and Cordova (such as PowerApps), can use this interface (or the more complex AudioConfig interface from Speech SDK) to implement microphone, even their platform does not support Web Audio API.

We should publicize this interface and write a sample.

We already have a mock microphone input in our test harness which use createAudioConfig with ArrayBuffer.

[feature-request]