Server wasm compatibility (#15)

* add axum sse example

* fix: make the sse axum folder name correct

* feat: add common modules for Axum SSE example

This commit adds supporting modules for the Axum Server-Sent Events (SSE) example:
- Added `counter.rs` with a simple counter router implementation
- Added `jsonrpc_frame_codec.rs` for decoding JSON-RPC frames
- Created a `mod.rs` to expose these modules
- Removed the previous SSE example configuration from Cargo.toml

* refactor: remove main.rs and update Cargo.toml for WASM compatibility

This commit makes two key changes:
1. Removes the main.rs file and make it a example
2. Add a wasi_std_io example

* refactor: simplify WASI I/O handling in example and fmt

Merged AsyncInputStream and AsyncOutputStream into a single WasiFd struct with std_in() and std_out() methods, reducing code duplication and improving clarity of the WASI standard I/O example.

* move examples to root

crates/mcp-server/Cargo.toml

@@ -14,7 +14,7 @@ mcp-macros = { workspace = true }
 serde = { version = "1.0.216", features = ["derive"] }
 serde_json = "1.0.133"
 schemars = "0.8"
-tokio = { version = "1", features = ["full"] }
+tokio = { version = "1", features = ["io-util"] }
 tower = { version = "0.4", features = ["timeout"] }
 tower-service = "0.3"
 futures = "0.3"