Add status line at bottom in garden dev

[edvald]

Currently it doesn't quite feel clear that the command is waiting for code changes.

We should at least add a fixed line that says something like "Waiting for changes to code" (like we had in our prototype), but it would be even better if the line changes when processing is happening. For that we'd need to rig some basic event emitter, but we'll want to do that anyway and we can keep it simple to start.

@eysi09 this one might be for you :)