Send box in speech listening mode don't auto scroll to far right

[compulim]

Repro steps:

1. Resize Web Chat window to be as narrow as possible without clipping
2. Click on microphone button
3. Say a very long sentence, like, "A quick brown fox jumped over the lazy dogs"

Expected: when the intermediate result is shown, Web Chat should keep the latest words on the screen by scrolling right
Actual: we only show the first few words, clipped everything else

Investigations:

• We move caret with selectionStart = selectionEnd = value.length
  • This only works when the send box is focused
  • UX-wise, we stop listening when the send box is focused
• When speech start, turn into a single-line
  • Change the parent to be scrollable, and auto-scroll to far right

I think a better solution is provide multi-line support.

[corinagum]

Related to #124