chore: add LICENSE, add missing metadata, clean up dependencies & use dev-dependencies, document choices

src/error.rs

@@ -37,9 +37,6 @@ pub enum GameError {
     #[error("IO error: {0}")]
     Io(#[from] io::Error),
 
-    #[error("Serialization error: {0}")]
-    Serialization(#[from] serde_json::Error),
-
     #[error("Invalid state: {0}")]
     InvalidState(String),
 }