Copy doc comments from Rust to JS (#265)

* backend comments complete

* better matching

* gen comments

* Add example

* Move test bindings gen to own fn

* move build step into build fn

* add fn to read js, refactor gen_bindings/test to allow for this

* Add comments test

* Update readmes

* add comments to travis

* fix broken tests

* +x on build.sh

* fix wbg cmd in build.sh

* Address fitzgen's comments

examples/comments/webpack.config.js

@@ -0,0 +1,11 @@
+const path = require('path');
+
+module.exports = {
+  entry: "./index.js",
+  output: {
+    path: path.resolve(__dirname, "dist"),
+    filename: "index.js",
+  },
+  mode: "development",
+  devtool: 'source-map',
+};