Added example notebook for alexatm20b in jumpstart (#3665)

* Added example notebook for alexatm20b in jumpstart

* AlexaTM 20b notebook: Minor typo fix

Co-authored-by: atqy <[email protected]>

Author: vivekmadan2

README.md

@@ -112,7 +112,7 @@ These examples provide quick walkthroughs to get you up and running with Amazon
 - [JumpStart Machine Translation](introduction_to_amazon_algorithms/jumpstart_machine_translation) demonstrates how to translate text from one language to another language in JumpStart.
 - [JumpStart Named Entity Recognition](introduction_to_amazon_algorithms/jumpstart_named_entity_recognition) demonstrates how to identify named entities such as names, locations etc. in the text in JumpStart.
 - [JumpStart Text to Image](introduction_to_amazon_algorithms/jumpstart_text_to_image) demonstrates how to generate image conditioned on text in JumpStart.
-
+- [In-context learning with AlexaTM 20B](introduction_to_amazon_algorithms/alexatm20b) demonstrates how to use AlexaTM 20B for in-context-learning in JumpStart.
 ### Amazon SageMaker RL
 
 The following provide examples demonstrating different capabilities of Amazon SageMaker RL.