doc: adding --version argument in example (#214)

Author: AllanZhengYP

Diff for: CONTRIBUTING.md

@@ -131,12 +131,12 @@ Options:
 For example, if you would like to create a DynamoDB client for browser-like runtime, the command will be like:
 
 ```
-node ./packages/package-generator/build/cli.js client --model models/dynamodb/2012-08-10/service-2.json --runtime browser --smoke models/dynamodb/2012-08-10/smoke.json
+node ./packages/package-generator/build/cli.js client --model models/dynamodb/2012-08-10/service-2.json --runtime browser --smoke models/dynamodb/2012-08-10/smoke.json --version 0.1.0-preview.1
 ```
 
 [issues]: https://github.com/aws/aws-sdk-js-v3/issues
 [pr]: https://github.com/aws/aws-sdk-js-v3/pulls
 [license]: http://aws.amazon.com/apache2.0/
 [cla]: http://en.wikipedia.org/wiki/Contributor_License_Agreement
 [AWS service models]: https://github.com/aws/aws-sdk-js-v3/tree/master/models
-[conventional commits]: https://www.conventionalcommits.org/
+[conventional commits]: https://www.conventionalcommits.org/