support for prettier_d_slim

[hood]

As title implies, it'd be great to support prettier_d_slim (ref.: https://github.com/mikew/prettier_d_slim), which is a faster prettier drop-in replacement (it's basically still prettier, but running on a background daemon service).

[slalomzacharyd]

Aaaaah, this exists because because prettier_d isn't supported anymore by the author.