Feature request: select the fastest Surfshark server

[bgwallace]

What's the feature 🧐

Please add a new docker environment variable that can be passed into the gluetun container which tells gluetun to automatically select the fastest Surfshark VPN server. Preferably, the env var can also be used to select the fastest United States VPN server.

Extra information and references

I'm using the Wireguard protocol.

This issue may be related to a similar feature request found in #719.

[github-actions]

@qdm12 is more or less the only maintainer of this project and works on it in his free time.
Please:

• do not ask for updates, be patient
• 👍 the issue to show your support instead of commenting
  @qdm12 usually checks issues at least once a week, if this is a new urgent bug,
  revert to an older tagged container image