add version logging to startup log messages for better troubleshooting

main.go

@@ -1,7 +1,15 @@
 package main
 
-import "github.com/dominicbreuker/pspy/cmd"
+import (
+	"fmt"
+
+	"github.com/dominicbreuker/pspy/cmd"
+)
+
+var version string
+var commit string
 
 func main() {
+	fmt.Printf("pspy - version: %s - Commit SHA: %s\n", version, commit)
 	cmd.Execute()
 }