Documentation and usage example for sieve script

packages/alias-to-sieve/README.md

@@ -5,8 +5,10 @@ Given an alias file `testdata/simple.aliases` that contains lines of redirects o
 If you don't define a fqdn along any of the addresses, the default domain from your commandline input will be appended.
 
 An example using the testdata directory of this repository:
-```
+```bash
 $ ./alias_to_sieve testdata/simple.aliases example.com
+```
+```sieve
 require ["variables", "copy", "vnd.stalwart.expressions", "envelope", "editheader"];
 
 let "i" "0";