Updated invoke utest task documentation to give example of running

selected test suites and test cases

Author: emanlove

tasks.py

@@ -207,6 +207,10 @@ def atest(ctx, suite=None):
 
     Args:
         suite: Select which suite to run.
+    
+    Example:
+        inv utest --suite keywords/test_browsermanagement.py
+        inv utest --suite keywords/test_selenium_options_parser.py::test_create_chrome_with_options
     """
     command = "python atest/run.py headlesschrome"
     if suite: