Show a notifier when it's required to restart server #509

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Feature request

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What problem does this feature solve?

https://github.com/saberland/saber/blob/83c18a706637fedccdbe0ad34566218dc5780d94/packages/saber/lib/plugins/extend-node-api.js#L89

People often modify saber-config.js, saber-node.js and forget to restart server.

How should this be implemented in your opinion?

Maybe use https://www.npmjs.com/package/node-notifier, and expose it in saber-utils package