Add Counter Contract Call Example to Miden Demo Site

Assuming there is a counter contract deployed on testnet, we should add an example to the miden demo website to show users how to interact with existing smart contracts on chain. This tickets assumes also that we double check the interface of the miden wallet connect functionality and ensure it's up to date with the latest client code.

Find the Miden demo website repository and locate the code for wallet connect functionality. Check the latest Miden client code to verify the interface. Add an example of interacting with a deployed counter contract on testnet to the site's examples section.

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