Implement Into<CaptureError> for the default server function error type (#4205)

* implement Into<CaptureError> for the server function error type

* document the server function error type

* fix tests

packages/server/src/lib.rs

@@ -50,7 +50,7 @@
 //! }
 //!
 //! #[server(GetServerData)]
-//! async fn get_server_data() -> Result<String, ServerFnError> {
+//! async fn get_server_data() -> ServerFnResult<String> {
 //!     Ok("Hello from the server!".to_string())
 //! }
 //! ```