README: add repo activity trends widget (#47139)

README.md

@@ -98,6 +98,13 @@ Contributions are welcomed and greatly appreciated. You can get started with one
 
 Every contributor is welcome to claim your contribution swag by filling in and submitting this [form](https://forms.pingcap.com/f/tidb-contribution-swag).
 
+<a href="https://next.ossinsight.io/widgets/official/compose-activity-trends?repo_id=41986369" target="_blank" style="display: block" align="center">
+  <picture>
+    <source media="(prefers-color-scheme: dark)" srcset="https://next.ossinsight.io/widgets/official/compose-activity-trends/thumbnail.png?repo_id=41986369&image_size=auto&color_scheme=dark" width="822" height="auto">
+    <img alt="Activity Trends of pingcap/tidb - Last 28 days" src="https://next.ossinsight.io/widgets/official/compose-activity-trends/thumbnail.png?repo_id=41986369&image_size=auto&color_scheme=light" width="822" height="auto">
+  </picture>
+</a>
+
 ## Case studies
 
 - [Case studies in English](https://www.pingcap.com/customers/)