Replace fontawesome cdn by react-fontawesome

[vincentfretin]

This closes #692
Some icons slightly changed.

Remaining to do:

• Regression for the collapsible panel when clicking on clipboard icon
• save icon
• icons for types camera: 'fa-camera', mesh: 'fa-cube', light: 'fa-lightbulb-o', text: 'fa-font'

[vincentfretin]

Before:

After:

[vincentfretin]

I replaced clipboard by clipbard-copy mainly because I couldn't figure out how to stop the click event propagating and collapse the panel. Switching to clipboard-copy reduce a bit the bundle size:
https://bundlephobia.com/package/clipboard@2.0.11 9kB minified
https://bundlephobia.com/package/clipboard-copy@4.0.1 838B minified

We removed downloading https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css here, so 27K less to download as well.

Before this PR:
483K aframe-inspector.min.js
After this PR:
551K aframe-inspector.min.js

increasing bundle to 68kB, wait this doesn't line up, I would had expected 490K maybe.
I confirm bundling without clipboard-copy is 550K.
So it's just the FontAwesomeIcon component that is 60K? That's crazy.
I'll investigate further later, I'll probably create a simple Icon React component just to render the svg. I put this PR back in draft.

Also just to confirm this wasn't due to bad tree shaking, I replaced

import {
  faCamera,
  faCube,
  faFont,
  faLightbulb
} from '@fortawesome/free-solid-svg-icons';

to

import { faCamera } from '@fortawesome/free-solid-svg-icons/faCamera';
import { faCube } from '@fortawesome/free-solid-svg-icons/faCube';
import { faFont } from '@fortawesome/free-solid-svg-icons/faFont';
import { faLightbulb } from '@fortawesome/free-solid-svg-icons/faLightbulb';

the bundle increased by 3KB TT.

[dmarcos]

Thanks so much!