Editor proxy fails to bind to HTTP port on Linux

[flaki]

subo compute deploy core --local, as described on the "Run Compute Locally" section of the quickstart will fail on at least Linux not being able to bind the proxy to the default (privileged) :80 HTTP port:

⏩ START: installing...
Container suborbital-scc-control-plane-1  Created
Container suborbital-scc-atmo-1  Created
Container suborbital-scc-builder-1  Created
Container suborbital-scc-control-plane-1  Starting
Container suborbital-scc-builder-1  Starting
Container suborbital-scc-builder-1  Started
Container suborbital-scc-control-plane-1  Started
Container suborbital-scc-atmo-1  Starting
Container suborbital-scc-atmo-1  Started
ℹ️  use `docker ps` and `docker-compose logs` to check deployment status

PROXY: local tunnel to function editor starting
2022/08/09 12:38:22 listen tcp :80: bind: permission denied

There is a --proxy-port flag to change the default port, but it's actually not mentioned until the next page of the docs.

Not sure how this works on Mac OS, but I would argue that changing the default port to a non-privileged port would be preferable beyond making this purely a documentation issue? I guess we are doing this so that http://local.suborbital.network does not need a port defined but is that really needed/worth it?

cc @cohix @ospencer @LauraLangdon