Design: Switching input mode

User story

Today, we mix typing and speech into the send box.

The end-user is not very indicative on whether the microphone is recording or not, especially without a waveform animation.

Please look at #1839 when working on this.

Alternatives

Today, we mix the input via keyboard and speech into a single input box.

Other implementations

Send box in Cortana and Siri can be either for keyboard or speech, but not hybrid.

Potential implementation

Tomorrow, we could use the microphone button to switch between 2+ types of input. And the end-user should has a very clear indication on what type of inputs they are using.

What this will fix?

• Synthesize all bot responses
  • Ability to synthesize all bot responses are very popular asks
• Synthesize proactive messages
  • When the user switch to speech mode, we can prime Web Audio API thru user gesture. This will enable synthesizing all proactive messages (#2474)
• Synthesize bot responses on file uploads
  • We also need to cater about file upload. If the user is in microphone input mode, they should still be able to upload files (e.g. mobile scenario). And the bot responses will be synthesized (#2474).
• #2568

[Enhancement]