On each PR, deploy artifacts

[amaury1093]

As discussed with @sjeohp, we could build some stuff on each PR to allow easy testing:

• deploy each PR's light-apps to e.g. substrate-light-ui-pr-244-somehash.netifly.com (or any other provider, needs to be http though)
• build the extension into a zip file, and store the artifacts in Github Actions (done in ci: Create a draft release with the extension #947)

[amaury1093]

We would need to deploy to a provider that provides http (not S), because of the no-ws-from-https problem.

From what I quickly saw, netlify and now.sh only allow https, but surge might work: https://surge.sh/help/using-https-by-default