v3.20.0

## Bug fixes

- IPVanish: certificate validation option fixed
- Fix OpenVPN restart logic
  - Remove OpenVPN eventual deadlock after a restart
  - Fix OpenVPN run loop panicing about log streams after one or more internal openvpn restart
- Shutdowns of subprograms (openvpn and unbound) are handled by the Go program
  - Openvpn and Unbound do not receive OS signals
  - Openvpn and Unbound run in a different process group than the entrypoint
  - Openvpn and Unbound are gracefully shutdown by the entrypoint
  - Update golibs with a modified `github.com/qdm12/golibs/command` package
  - Update `github.com/qdm12/dns` to `v1.9.0` where Unbound is launched in its own group
- Fix events routing behavior if `VERSION_INFORMATION=off`
- Behavior when exiting at boot
  - Events routing routine exits when gluetun stops
  - Remove deadlock on dns shutdown

## Features

- OpenVPN pull filter for ipv6 options if `OPENVPN_IPV6=off`
- Update servers information:
  - ProtonVPN
  - IPVanish
- Upgrade to Alpine 3.14
- Clean suffix new line(s) for credentials

## Documentation

- Add [Youtube video](https://youtu.be/0F6I03LQcI4)
- Simplify metdata and move it at top of readme

## Maintenance

### Dockerfile

- Download `golangci-lint` from `qmcgaw/binpot`
- `xcputranslate` version as build argument

### Readme

- Use native markdown code for svg title image instead of HTML's `<svg>`

### Logs

- Deduplicate error logs for `goshutdown`
- Remove outdated auth error warning about PIA

### Asynchronous logic

- Make all loop's `SetStatus` context aware
- Rework DNS run loop
  - Fix fragile user triggered logic
  - Simplify state logic
- Rework Openvpn run loop
- Rework openvpn unhealthy triggered restart to be in the healthcheck loop instead of in the openvpn loop