Response generator responses with multimedia elements (#6323)

* Use rules for greet, goodbye & challenge

* Convert nlu & stories to yml

* Add '-' in front of examples

* Add 'y' , 'n' to affirm & deny intents

* Remove 'greet -> utter_greet' rule, and use in stories instead

* implement yaml response format as well as extended response format

extended response format adds the ability to add images, buttons, ... to responses generated from the response selector. the format is the same as we use for utter templates in the domain.

* code style improvement

* fixed linter error

* fixed some more test and renamed nlg_stories to responses

* fixed typing issue

* fixed more types

* fixed tests

* Update training_data.py

* fixed import errror

* fixed remaining tests

* fixed name error

* Update rules.yml

* added tests for responses

* added changelog entry

* updated documentation

* applied review suggestions

* integrated review comments

* fixed typing issue

Co-authored-by: Arjaan Buijk <[email protected]>
Co-authored-by: Arjaan Buijk <[email protected]>
Co-authored-by: Roberto <[email protected]>

test_rasa_interactive.py

@@ -8,6 +8,7 @@
 
 import rasa
 from rasa.cli import interactive, train
+from tests.conftest import DEFAULT_NLU_DATA
 
 
 def test_interactive_help(run: Callable[..., RunResult]):
@@ -110,7 +111,7 @@ def test_train_core_called_when_no_model_passed_and_core(
             "--config",
             default_stack_config,
             "--stories",
-            "examples/moodbot/data/stories.md",
+            "examples/moodbot/data/stories.yml",
             "--domain",
             "examples/moodbot/domain.yml",
         ]
@@ -136,13 +137,7 @@ def test_no_interactive_without_core_data(
     interactive.add_subparser(sub_parser, [])
 
     args = parser.parse_args(
-        [
-            "interactive",
-            "--config",
-            default_stack_config,
-            "--data",
-            "examples/moodbot/data/nlu.md",
-        ]
+        ["interactive", "--config", default_stack_config, "--data", DEFAULT_NLU_DATA,]
     )
     interactive._set_not_required_args(args)