feat: check for slirp4netns tool during setup (needed for rootless Podman)

Makefile

@@ -9,7 +9,9 @@ info:
 
 setup:
 	@echo "I checking for tools"
-	@for binary in go go-bindata tmux node yarn npx podman pexec inotifyloop inotifywait newuidmap; do \
+	@for binary in go go-bindata tmux node yarn npx \
+			 pexec inotifyloop inotifywait \
+	     podman newuidmap slirp4netns; do \
 		echo -n "  $$binary: " ; \
 		if ! which "$$binary"; then \
 			echo "not found" ;\