fix: add serde_json to sherpaonnx feature deps

sherpaonnx_engine.rs uses serde_json for parsing credentials JSON

Author: willwade

Cargo.toml

@@ -15,7 +15,7 @@ crate-type = ["cdylib", "staticlib", "lib"]
 default = ["system", "cloud", "sherpaonnx"]
 system = ["speech-dispatcher"]
 cloud = ["reqwest", "serde_json", "base64", "speechmarkdown-rust", "tungstenite", "uuid", "url"]
-sherpaonnx = ["sherpa-onnx"]
+sherpaonnx = ["sherpa-onnx", "serde_json"]
 tungstenite = ["dep:tungstenite"]
 uuid = ["dep:uuid"]
 url = ["dep:url"]