add example for scenario spec test

nbr-examples/src/test/resources/scripts/examples/basicdiag.md

@@ -0,0 +1,21 @@
+
+*command line:*
+```bash
+# command line
+nb script basic_diag.js
+```
+*scenario script:*
+```javascript
+// file: basic_diag.js
+basic_diag = params.withOverrides({
+    "alias" : "basic_diag",
+    "driver" : "diag"
+});
+
+print('starting activity basic_diag');
+scenario.start(basic_diag);
+```
+*expected output:*
+```text
+starting activity basic_diag
+```