wireguard-tools: add wireguard_watchdog script

wireguard-tools: add wireguard_watchdog script

This watchdog script tries to re-resolve hostnames for inactive WireGuard peers.
Use it for peers with a frequently changing dynamic IP.
persistent_keepalive must be set, recommended value is 25 seconds.
Run this script from cron every minute:
echo '* * * * * /usr/bin/wireguard_watchdog' >> /etc/crontabs/root

Signed-off-by: Aleksandr V. Piskunov <aleksandr.v.piskunov@gmail.com>
[bump the package release]
Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>