Add Java 11 Kokoro config (#487)

* Add java 11 test config

* Update README badge to use Java 11 instead of Java 10

Author: chingor13

.kokoro/continuous/java11.cfg

@@ -0,0 +1,7 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Configure the docker image for kokoro-trampoline.
+env_vars: {
+  key: "TRAMPOLINE_IMAGE"
+  value: "gcr.io/cloud-devrel-kokoro-resources/java11"
+}

.kokoro/presubmit/java11.cfg

@@ -0,0 +1,7 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Configure the docker image for kokoro-trampoline.
+env_vars: {
+  key: "TRAMPOLINE_IMAGE"
+  value: "gcr.io/cloud-devrel-kokoro-resources/java11"
+}

README.md

@@ -42,7 +42,7 @@ Java Version | Status
 ------------ | ------
 Java 7 | [![Kokoro CI](https://storage.googleapis.com/cloud-devrel-public/java/badges/google-http-java-client/java7.svg)](https://storage.googleapis.com/cloud-devrel-public/java/badges/google-http-java-client/java7.html)
 Java 8 | [![Kokoro CI](https://storage.googleapis.com/cloud-devrel-public/java/badges/google-http-java-client/java8.svg)](https://storage.googleapis.com/cloud-devrel-public/java/badges/google-http-java-client/java8.html)
-Java 10 | [![Kokoro CI](https://storage.googleapis.com/cloud-devrel-public/java/badges/google-http-java-client/java10.svg)](https://storage.googleapis.com/cloud-devrel-public/java/badges/google-http-java-client/java10.html)
+Java 11 | [![Kokoro CI](https://storage.googleapis.com/cloud-devrel-public/java/badges/google-http-java-client/java11.svg)](https://storage.googleapis.com/cloud-devrel-public/java/badges/google-http-java-client/java11.html)
 
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