The latest version installed by npm is different than what is in the repo

**Actual Behaviour**

When I run `npm install` as directed in the README, I get the version 0.2.40 installed. This version doesn't handle the `docker` flag mentioned in the README as well, and in the documentation at https://www.serverless.com/plugins/serverless-dynamodb-local.

**Expected Behaviour**

I expect the installation by npm to be same like a tag or a branch in this repo so that I can find out which version is having which feature. At the moment I cannot use the docker feature because it is not supported in version 0.2.40 that is available by npm install. Furthermore, I cannot find a tag or a branch with the value 0.2.40. The version 0.2.40 though is still the current version in the package.json file in the repo.

**Steps to reproduce it**

1. Run `npm install serverless-dynamodb-local`. Notice the installed version will be 0.2.40.
2. Run `serverless dynamodb start --docker`
3. An error stating that the flag docker is not recognizable.
4. Find the installed packages for serverless-dynamodb-local and examine the README file.
5. The README file doesn't include the docker flag which indicates a different version than what is currently in the repo and the online documentation.

**Would you like to work on the issue?**

Yes. With some guidance.

Compare the repository's package.json and README with the 0.2.40 package installed by npm, starting with the documented npm install and serverless dynamodb start --docker steps. Confirm where the published package diverges from the repository, then verify that the published version and documentation expose the same docker behavior and version information.

Written by the indexing model from the issue text.