Vendor dependencies

Let's see how I like this workflow.

vendor/wasm-bindgen-backend/Cargo.toml

@@ -0,0 +1,49 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+name = "wasm-bindgen-backend"
+version = "0.2.83"
+authors = ["The wasm-bindgen Developers"]
+description = """
+Backend code generation of the wasm-bindgen tool
+"""
+homepage = "https://rustwasm.github.io/wasm-bindgen/"
+documentation = "https://docs.rs/wasm-bindgen-backend"
+license = "MIT/Apache-2.0"
+repository = "https://github.com/rustwasm/wasm-bindgen/tree/master/crates/backend"
+
+[dependencies.bumpalo]
+version = "3.0.0"
+
+[dependencies.log]
+version = "0.4"
+
+[dependencies.once_cell]
+version = "1.12"
+
+[dependencies.proc-macro2]
+version = "1.0"
+
+[dependencies.quote]
+version = "1.0"
+
+[dependencies.syn]
+version = "1.0"
+features = ["full"]
+
+[dependencies.wasm-bindgen-shared]
+version = "=0.2.83"
+
+[features]
+extra-traits = ["syn/extra-traits"]
+spans = []