Add etcher apt-repo because the one provided by balena is down

[alsotoes]

Issue https://github.com/balena-io/etcher/issues/4059 describes why the main public etcher repo provided by Balena stopped working.

• [ ] Create apt-repo on US repo (https://us.mirrors.headup.ws/)
• [ ] Sign deb package
• [x] Add GPG key to gist.github.com
• [x] Change to Cherokee Webserver
• [ ] Share with the community
• [ ] Replicate repo for LATAM (https://cl.mirrors.headup.ws/)

[alsotoes]

URL to complete this:

• public key
• earthly howto
• DO howto