chore: setup release-please to update generator version in generation configuration (#2819)

In this PR:
- Setup release-please to update the generator version in the
`generation_config.yaml`.

Author: JoeWang1127

.github/release-please.yml

@@ -3,4 +3,4 @@ bumpMinorPreMajor: true
 handleGHRelease: true
 primaryBranch: main
 manifest: true
-extraFiles: ["WORKSPACE", ".cloudbuild/graalvm/cloudbuild.yaml", ".cloudbuild/graalvm/cloudbuild-test-a.yaml", ".cloudbuild/graalvm/cloudbuild-test-b.yaml", ".cloudbuild/library_generation/cloudbuild-library-generation-release.yaml" ]
+extraFiles: ["WORKSPACE", ".cloudbuild/graalvm/cloudbuild.yaml", ".cloudbuild/graalvm/cloudbuild-test-a.yaml", ".cloudbuild/graalvm/cloudbuild-test-b.yaml", ".cloudbuild/library_generation/cloudbuild-library-generation-release.yaml", "generation_config.yaml"]

generation_config.yaml

@@ -1,4 +1,4 @@
-gapic_generator_version: 2.40.2-SNAPSHOT
+gapic_generator_version: 2.40.2-SNAPSHOT # {x-version-update:gapic-generator-java:current}
 googleapis_commitish: 3d50414a7ff3f0b8ffe8ad7858257396e4f18131
 template_excludes:
 - .github/*

release-please-config.json

@@ -5,7 +5,14 @@
   "group-pull-request-title-pattern": "chore(${branch}): release ${version}",
   "packages": {
     ".": {
-      "extra-files": ["WORKSPACE", ".cloudbuild/graalvm/cloudbuild.yaml", ".cloudbuild/graalvm/cloudbuild-test-a.yaml", ".cloudbuild/graalvm/cloudbuild-test-b.yaml", ".cloudbuild/library_generation/cloudbuild-library-generation-release.yaml"]
+      "extra-files": [
+        "WORKSPACE",
+        ".cloudbuild/graalvm/cloudbuild.yaml",
+        ".cloudbuild/graalvm/cloudbuild-test-a.yaml",
+        ".cloudbuild/graalvm/cloudbuild-test-b.yaml",
+        ".cloudbuild/library_generation/cloudbuild-library-generation-release.yaml",
+        "generation_config.yaml"
+      ]
     }
   }
 }