[storage]Add a summary migrationguide for storage sdks. (Azure#19619)

* Add a summary migrationguide for storage sdks.

* Resolve PR comments.

Author: EmmaZhu

sdk/storage/MigrationGuide.md

@@ -0,0 +1,10 @@
+# Guide for migrating to v12 storage SDKs from `azure-storage`
+
+Below are links to detailed guides to migrate from the legacy `azure-storage` package to the latest versions of `@azure/storage-blob`, `@azure/storage-file-share`, `@azure/storage-queue` and `@azure/data-tables`.
+
+| Package                                                                              | Version | Description                                     | Migration Guide Links                                                                                                                                                       |
+| ------------------------------------------------------------------------------------ | ------- | ----------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| [@azure/storage-blob](https://www.npmjs.com/package/@azure/storage-blob)             | v12     | The next generation SDK for Azure Blob Storage  | [Migration Guide from `azure-storage` to `@azure/storage-blob`](https://github.com/Azure/azure-sdk-for-js/blob/main/sdk/storage/storage-blob/MigrationGuide.md)             |
+| [@azure/storage-queue](https://www.npmjs.com/package/@azure/storage-queue)           | v12     | The next generation SDK for Azure Queue Storage | [Migration Guide from `azure-storage` to `@azure/storage-queue`](https://github.com/Azure/azure-sdk-for-js/blob/main/sdk/storage/storage-queue/MigrationGuide.md)           |
+| [@azure/storage-file-share](https://www.npmjs.com/package/@azure/storage-file-share) | v12     | The next generation SDK for Azure Files         | [Migration Guide from `azure-storage` to `@azure/storage-file-share`](https://github.com/Azure/azure-sdk-for-js/blob/main/sdk/storage/storage-file-share/MigrationGuide.md) |
+| [@azure/data-tables](https://www.npmjs.com/package/@azure/data-tables)               | v12     | The next generation SDK for Azure Table Storage | [Migration Guide from `azure-storage` to `@azure/data-tables`](https://github.com/Azure/azure-sdk-for-js/blob/main/sdk/tables/data-tables/MigrationGuide.md)                |