Add syntax highlighting to readme.md

README.MD

@@ -33,7 +33,7 @@ Close the editor. This will call the script every 4 hours. (Or should. I'll veri
 
 Now we need to create the shell script it calls; `/usr/local/bin/voipbpl.sh`
 
-```
+```bash
 #!/bin/bash
 
 # Check if chain exists and create one if required