Add CompactBlock scanning to WASM backend

zcash-client-backend-wasm/Cargo.toml

@@ -11,7 +11,10 @@ crate-type = ["cdylib", "rlib"]
 default = ["console_error_panic_hook"]
 
 [dependencies]
+hex = "0.3"
+protobuf = "2"
 wasm-bindgen = "0.2"
+web-sys = { version = "0.3", features = ["console"] }
 
 # The `console_error_panic_hook` crate provides better debugging of panics by
 # logging them with `console.error`. This is great for development, but requires