Add Apache SkyWalking to the list of users (#2967)

Author: kezhenxu94

docs/index.md

@@ -118,6 +118,7 @@ testImplementation('org.testcontainers:mysql') //no version specified
 * [Marquez](https://marquezproject.github.io/marquez) - PostgreSQL integration testing
 * [Transferwise](https://transferwise.com/) - Integration testing for different RDBMS, kafka and micro services
 * [XWiki](https://xwiki.org) - [Testing XWiki](https://dev.xwiki.org/xwiki/bin/view/Community/Testing/DockerTesting/) under all [supported configurations](https://dev.xwiki.org/xwiki/bin/view/Community/SupportStrategy/)
+* [Apache SkyWalking](http://github.com/apache/skywalking) - End-to-end testing of the Apache SkyWalking, and plugin tests of its subproject, [Apache SkyWalking Python](http://github.com/apache/skywalking-python), and of its eco-system built by the community, like [SkyAPM NodeJS Agent](http://github.com/SkyAPM/nodejs)
 
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