Support editing lix scripts.

[back2dos]

Dunno if this is achievable without bending over backward, but it would be nice if there were support for editing lix scripts, see: https://github.com/lix-pm/lix.client#scripting

I think the ideal solution would be, that when the user navigates to a "script file", i.e. one starting with //!, to launch a second haxe server with the configuration taken from the script (my thinking is that using the current server might be annoying when going back and forth between the scripts and the "actual" project). And I suppose it'd make sense for the build command to map to npx lix CurrentScript in that case, although I suppose that's the most gimmicky part of this idea ^^