Add `reload` command to validate and reload configuration

[DiTsi]

Implement a reload command for IMPulse, similar in behavior to nginx -s reload.

Expected behavior:

When executed, the command should:

1. Validate the current impulse.yml configuration file.
2. If the configuration is valid, reload the running configuration without restarting the process.
3. If the configuration is invalid, return an error and do not apply changes.