Implement auto reload when files changes

[vishr]

Migrated from labstack/echo#277

[Fantastitech]

This would be a very useful feature to have baked into Echo with some sort of development flag, or as mentioned when Debug is enabled. There was a third-party echo-livereload package but there was a breaking change in Echo that made it incompatible. Most generic implementations require proxying requests which isn't ideal.

I think this is a good feature to have natively implemented rather than just be a recipe. It's a small quality of life improvement that makes a big difference when making a lot of small changes to an application.

[skunkworker]

I've used air with the default .air.conf without any issues so far.

[thebigbone]

Is there any update on this? Restarting the server every time is tedious, atleast for local development