Add Counter Contract project to examples

[greenhat]

After #436 is merged.

Motivation

We need a new example project in the examples/ directory demonstrating how to write and deploy a simple counter contract using the Miden SDK. This will complement the existing storage-example project by showcasing the account API in action and providing a reference implementation for developers.

Implementation

1. Create a new folder: examples/counter-contract
2. Scaffold a Rust-based client project in that folder, following the pattern in examples/storage-example:
   • Include Cargo.toml, src/lib.rs, and WIT files.
3. Write the contract code inspired by the tutorial's MASM code at miden-tutorials.
4. Add documentation (README.md) in the counter-contract folder explaining:
   • How to build the contract.
   • How to run the example client (link to the miden-tutorials.
5. Add a counter_contract test in tests/integration/src/rust_masm_tests/examples.rs that compiles it and checks the code and AccountComponentMetadata from the Miden package.

[greenhat]

Following the discussion with @partylikeits1983

[partylikeits1983]

@greenhat Using your storage example as a reference, this is the counter rust contract that I wrote: https://github.com/partylikeits1983/compiler-hackathon-counter/tree/main/examples/counter-example

The only part that is missing is the call to increment the nonce.