Fix wasm deps

Cargo.toml

@@ -71,7 +71,7 @@ wasm-bindgen-test = "0.3"
 # use std to retrieve OS error descriptions
 std = []
 # Enable opt-in backends
-opt_in = []
+opt_in = ["dep:wasm-bindgen", "dep:js-sys"]
 # Unstable feature to support being a libstd dependency
 rustc-dep-of-std = ["dep:compiler_builtins", "dep:core"]