Add generate smart contract client information

[limemloh]

• [x] The developer documentation needs to include a link to the ccd-js-gen package with a description of what the package does.
• Tutorials using the JavaScript SDK and smart contract interaction should be rewritten to use generated clients.
  • [ ] Sponsored transactions.

[limemloh]

The remaining task here depends on a new release of the web wallet API.

[abizjak]

@Bargsteen I think it'd be great to include this in the "iterate on smart contract documentation epic".