chore: release 2.0.0 (#31)

* updated CHANGELOG.md [ci skip]

* updated package.json [ci skip]

* updated samples/package.json [ci skip]

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>

Author: release-please[bot]

document-ai/package.json

@@ -13,7 +13,7 @@
     "test": "mocha test/*.js --timeout 600000"
   },
   "dependencies": {
-    "@google-cloud/documentai": "^1.0.0",
+    "@google-cloud/documentai": "^2.0.0",
     "@google-cloud/storage": "^5.0.0"
   },
   "devDependencies": {