feat: hosts files automatic reloading when modified

[keuin]

Hello everyone, thanks for your great work!

I use cronjob to update my hosts file and need to react to updates as soon as possible. So I developed this feature.

This feature is disabled by default and controlled by boolean config field hostsFile.watchUpdates.

This is an early PR (and a feature request). I will test it in my homelab environment before marking it as ready. Please let me know if there are suggestions or requirements. Thank you.