add @growi/slack in slack-proxy

packages/slackbot-proxy/package.json

@@ -28,7 +28,8 @@
     "compression": "^1.7.4",
     "dotenv-flow": "^3.2.0",
     "mysql2": "^2.2.5",
-    "typeorm": "^0.2.31"
+    "typeorm": "^0.2.31",
+    "@growi/slack":"0.9.0-RC"
   },
   "devDependencies": {
     "@tsed/core": "^6.34.3",