Add generate_204 enpoint #272
Description
A well known generate_204 can be used for dns-prefetch and captive-portal detection on Wazigate.
More on that topic:
https://www.chromium.org/chromium-os/chromiumos-design-docs/network-portal-detection
https://developer.mozilla.org/en-US/docs/Web/Performance/dns-prefetch (related topic)
The https://waziup.io/ should implement such an endpoint https://waziup.io/generate_204, returning an empty response with status code 204 (No Content), mainly for usage with the Wazigate.