Add support to create a new agent through NPX

[nohe427]

** Please make sure you read the contribution guide and file the issues in the right place. ** Contribution guide.

Is your feature request related to a problem? Please describe.

Its kind of a pain to go to the documentation and copy and paste starter code with the ADK for Python offers the command adk create AGENT_NAME.

Describe the solution you'd like npx @google/adk --create AGENT_NAME

Describe alternatives you've considered

Python ADK command asks you to pick the language you want to use

Additional context

Genkit offers a really easy way to get started with a new template through their CLI. I would like to see something similar here.