feat: add pacman-contrib installer

internal/installers/pacman_contrib.go

@@ -0,0 +1,13 @@
+package installers
+
+import "github.com/developomp/pompup/internal/wrapper"
+
+func init() {
+	register(&Installer{
+		Name: "Pacman-contrib",
+		Desc: "pactree and other stuff",
+		Setup: func() {
+			wrapper.ParuOnce("pacman-contrib")
+		},
+	})
+}