[language-text] Update Readme about the gated preview feature (Azure#25228)

Author: minhanh-phan

sdk/cognitivelanguage/ai-language-text/README.md

@@ -38,7 +38,9 @@ Key links:
 Please see the [Migration Guide](https://github.com/azure/azure-sdk-for-js/blob/main/sdk/cognitivelanguage/ai-language-text/MIGRATION_ai_text_analytics.md) for detailed instructions on how to update application code from version 5.x of the AI Text Analytics client library to the new AI Language Text client library.
 
 ## What's New
-* [Abstractive Summarization](https://github.com/azure/azure-sdk-for-js/blob/main/sdk/cognitivelanguage/ai-language-text/Samples.md#abstractive-summarization)
+
+* [Abstractive Summarization](https://github.com/azure/azure-sdk-for-js/blob/main/sdk/cognitivelanguage/ai-language-text/Samples.md#abstractive-summarization):
+To get started, submit a request for access [here](https://aka.ms/applyforgatedsummarizationfeatures).
 * [Script Detection](https://github.com/azure/azure-sdk-for-js/blob/main/sdk/cognitivelanguage/ai-language-text/Samples.md#language-detection)
 * [Automatic Language Detection](https://github.com/azure/azure-sdk-for-js/blob/main/sdk/cognitivelanguage/ai-language-text/Samples.md#automatic-language-detection)
 * [Entity Resolutions](https://github.com/azure/azure-sdk-for-js/blob/main/sdk/cognitivelanguage/ai-language-text/Samples.md#entity-resolutions)

sdk/cognitivelanguage/ai-language-text/Samples.md

@@ -386,7 +386,9 @@ main();
 
 ### Abstractive Summarization
 
-Abstractive summarization generates a summary for the input articles. Abstractive summarization is different from extractive summarization in that extractive summarization is the strategy of concatenating extracted sentences from the input document into a summary, while abstractive summarization involves paraphrasing the document using novel sentences.
+Abstractive summarization generates a summary for the input articles. Abstractive summarization is different from extractive summarization in that extractive summarization is the strategy of concatenating extracted sentences from the input document into a summary, while abstractive summarization involves paraphrasing the document using novel sentences. 
+
+To get started, submit a request for access [here](https://aka.ms/applyforgatedsummarizationfeatures).
 
 ```javascript
 const { AzureKeyCredential, TextAnalysisClient } = require("@azure/ai-language-text");