Add sleep() function (close #83)

Signed-off-by: Ben Sherman <[email protected]>

modules/compiler/src/main/java/script/dsl/ScriptDsl.java

@@ -138,6 +138,11 @@ The directory where a module script is located (equivalent to `projectDir` if us
     """)
     void sendMail(Map<String,?> params);
 
+    @Description("""
+        Sleep for the given number of milliseconds.
+    """)
+    void sleep(long milliseconds);
+
     @Description("""
         Create a tuple object from the given arguments.
     """)