fix(protonvpn): authenticated servers data updating (#2878)

- `-proton-username` flag for cli update
- `-proton-password` flag for cli update
- `UPDATER_PROTONVPN_USERNAME` option for periodic updates
- `UPDATER_PROTONVPN_PASSWORD` option for periodic updates

Dockerfile

@@ -204,6 +204,8 @@ ENV VPN_SERVICE_PROVIDER=pia \
     UPDATER_PERIOD=0 \
     UPDATER_MIN_RATIO=0.8 \
     UPDATER_VPN_SERVICE_PROVIDERS= \
+    UPDATER_PROTONVPN_USERNAME= \
+    UPDATER_PROTONVPN_PASSWORD= \
     # Public IP
     PUBLICIP_FILE="/tmp/gluetun/ip" \
     PUBLICIP_ENABLED=on \