Add once-bin to edge (#70)

This package provides the ONCE tool (https://github.com/basecamp/once).
ONCE is a tool for easy self-hosting of Docker-based web applications.

pkgbuilds/edge/once-bin/.gitignore

@@ -0,0 +1,6 @@
+*
+!.gitignore
+!.SRCINFO
+!PKGBUILD
+!once-background.service
+!once.install