chore: adding docfx doclet resource (#259)

* chore: updating publish_javadoc to support docfx yml generation

* fix: reducing commit

Source-Author: Emily Ball <emilyball@google.com>
Source-Date: Mon Jan 25 13:29:09 2021 -0800
Source-Repo: googleapis/synthtool
Source-Sha: 3816b080296d4d52975079fd26c110dd26ba25af
Source-Link: googleapis/synthtool@3816b08

.kokoro/release/publish_javadoc.cfg

@@ -27,3 +27,6 @@ before_action {
     }
   }
 }
+
+# Downloads docfx doclet resource. This will be in ${KOKORO_GFILE_DIR}/<doclet name>
+gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/docfx"

synth.metadata

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-shared-dependencies.git",
-        "sha": "14caf406fd876f8ab43b35f319a23cb8bc177337"
+        "sha": "88e88fc322c9352d59bc6f07e8f8c6f5addd5add"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "6133907dbb3ddab204a17a15d5c53ec0aae9b033"
+        "sha": "3816b080296d4d52975079fd26c110dd26ba25af"
       }
     }
   ],