generate doc for database

Author: Feiyang1

package.json

@@ -50,7 +50,7 @@
     "lint:fix": "lerna run --scope @firebase/* --scope rxfire lint:fix",
     "size-report": "ts-node-script scripts/size_report/report_binary_size.ts",
     "modular-export-size-report": "ts-node-script scripts/size_report/report_modular_export_binary_size.ts",
-    "api-report": "lerna run --scope @firebase/*-exp --scope @firebase/firestore --scope @firebase/storage --scope @firebase/storage-types-exp api-report",
+    "api-report": "lerna run --scope @firebase/*-exp --scope @firebase/firestore --scope @firebase/storage --scope @firebase/storage-types --scope @firebase/database api-report",
     "docgen:exp": "ts-node-script scripts/exp/docgen.ts",
     "postinstall": "yarn --cwd repo-scripts/changelog-generator build",
     "sa": "ts-node-script repo-scripts/size-analysis/cli.ts"