link functions GitHub Readme to library reference overview

.openpublishing.publish.config.json

@@ -51,6 +51,12 @@
       "branch": "master",
       "branch_mapping": {}
     },
+    {
+      "path_to_root": "_functionsref",
+      "url": "https://github.com/Azure/azure-functions-java-library",
+      "branch": "master",
+      "branch_mapping": {}
+    },
     {
       "path_to_root": "preview/_mavenref",
       "url": "https://github.com/Microsoft/azure-maven-plugins/",

docs-ref-mapping/reference.yml

@@ -300,7 +300,7 @@
       - com.microsoft.azure.eventprocessorhost
   - name: Functions
     uid: azure.java.sdk.landingpage.services.functions
-    landingPageType: Service
+    href: ~/_functionsref/README.md
     items:
     - name: Runtime
       uid: azure.java.sdk.landingpage.services.runtime.functions