Use wasm-bindgen feature on ditto-codegen-js

[jmackie]

Available since ditto-lang/ditto@9cbfc7f

Does away with:

playground/ditto-web/Cargo.toml

Lines 25 to 28 in cd5185b

	# Not a direct dependency but we need to enable the `wasm-bindgen` feature.
	#
	# Sub-dependency features aren't supported: https://stackoverflow.com/a/65468297/17263155
	egg = { version = "0.9", features = ["wasm-bindgen"] }