Vendor dependencies

Let's see how I like this workflow.

vendor/wasm-bindgen/guide/src/examples/dom.md

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+# web-sys: DOM hello world
+
+[View full source code][code] or [view the compiled example online][online]
+
+[online]: https://rustwasm.github.io/wasm-bindgen/exbuild/dom/
+[code]: https://github.com/rustwasm/wasm-bindgen/tree/master/examples/dom
+
+Using `web-sys` we're able to interact with all the standard web platform
+methods, including those of the DOM! Here we take a look at a simple "Hello,
+world!" which manufactures a DOM element in Rust, customizes it, and then
+appends it to the page.
+
+## `Cargo.toml`
+
+You can see here how we depend on `web-sys` and activate associated features to
+enable all the various APIs:
+
+```toml
+{{#include ../../../examples/dom/Cargo.toml}}
+```
+
+## `src/lib.rs`
+
+```rust
+{{#include ../../../examples/dom/src/lib.rs}}
+```