Add an axum sse example (#12)

* 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

* move examples to root

* nit: remove extra newline here

examples/servers/Cargo.toml

@@ -17,6 +17,15 @@ tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 tracing-appender = "0.2"
 futures = "0.3"
 
+[dev-dependencies]
+axum = { version = "0.8", features = ["macros"] }
+tokio-util = { version = "0.7", features = ["io", "codec"]}
+rand = { version = "0.8" }
+
 [[example]]
 name = "counter-server"
 path = "src/counter_server.rs"
+
+[[example]]
+name = "axum"
+path = "src/axum.rs"