Some design tweaks to make voice-client-javascript more mobile friendly.

[philnash]

Description

• Changes layout to flex box
• Adds a break point to flow vertically on small screens
• Puts number and call button on far left/top of screen instead of the middle

It now looks like this on desktop:

And this on a thinner device:

Checklist

• I ran npm test locally and it passed without errors.
• I acknowledge that all my contributions will be made under the project's license.

[philnash]

Hey @craigsdennis, this was your function. What do you think about these changes?

(I can't request a review from you I'm afraid.)

[philnash]

On second thoughts, I still don't like this. I'm going to spend a bit of time at some point making this look nicer. I'm no designer, but this is overall too busy and I think I can do a bit better and keep all of the features.

[dkundel]

Are still going to keep working on this? :) Just checking in whether to merge this or not

[philnash]

@dkundel Ah, @craigsdennis told me that the quick start itself was getting a design makeover so was going to wait that out.