cli: Log connection errors during dx serve in desktop apps

[srid]

While debugging the dx cli for a hot-reload issue, I thought this would be useful to have. Let me know if I'm missing something! Previously, the if let(Ok... was silently ignoring connection errors.

Diff sans whitespace for review.

[ealmloff]

Hot reloading will try to connect when you run cargo run as well as dioxus serve --platform desktop. I added a note about the CLI for users who just use cargo.

Thank you!