readme: add region tags (#3421)

Adding region tags to include in Java Cloud Client Library docs on cloud.google.com

README.md

@@ -74,12 +74,13 @@ libraryDependencies += "com.google.cloud" % "google-cloud-storage" % "1.35.0"
 ```
 [//]: # ({x-version-update-end})
 
+// [START java_ides_links]
 If you're using IntelliJ or Eclipse, you can add client libraries to your project using these IDE plugins: 
 * [Cloud Tools for IntelliJ](https://cloud.google.com/tools/intellij/docs/client-libraries?utm_source=github&utm_medium=google-cloud-java&utm_campaign=ToolsforIntelliJ)
 * [Cloud Tools for Eclipse](https://cloud.google.com/eclipse/docs/libraries?utm_source=github&utm_medium=google-cloud-java&utm_campaign=ToolsforEclipse)
 
 Besides adding client libraries, the plugins provide additional functionality, such as service account key management. Refer to the documentation for each plugin for more details.
-
+// [END java_ides_links]
 These client libraries can be used on App Engine standard for Java 8 runtime and App Engine flexible (including the Compat runtime).  Most of the libraries do not work on the App Engine standard for Java 7 runtime. However, Datastore, Storage, and Bigquery should work.
 
 If you are running into problems with version conflicts, see [Version Management](#version-management).