add "cdk:diff" shortcut to package.json (#1342)

Author: knziiy

package.json

@@ -17,6 +17,7 @@
     "cdk:deploy": "npm -w packages/cdk run cdk deploy -- --all",
     "cdk:deploy:quick": "npm -w packages/cdk run cdk deploy -- --all --asset-parallelism --asset-prebuild=false --concurrency 3 --method=direct --require-approval never --force",
     "cdk:deploy:quick:hotswap": "npm -w packages/cdk run cdk deploy -- --all --asset-parallelism --asset-prebuild=false --concurrency 3 --method=direct --require-approval never --force --hotswap",
+    "cdk:diff": "npm -w packages/cdk run cdk diff -- --all",
     "cdk:destroy": "npm -w packages/cdk run cdk destroy -- --all",
     "cdk:lint": "npm -w packages/cdk run lint",
     "cdk:lambda-build-dryrun": "npm -w packages/cdk run lambda-build-dryrun",