Electron applications in Rust

It's 2020, and a lot has changed.

• With the advent of Webpack 5, the previous issues with using WASM in Electron have been vanquished. I can only assume some form of sorcery was involved. All examples have been updated to use the new version.
• wasm32-unknown-unknown targets are enabled for stable Rust, everything updated to 2018 edition
• The previous percy example has been removed. While work continues on the project, there haven't been any releases.
• binaryen has been removed.
• A new framework seed as been added as an example.
• The stdweb example has been freshened up:
  • Use #[wasm_bindgen(start)] to remove the app loader script
  • Don't use innerHTML, just set the text content directly.

Each app is a starter example, and can be run with yarn install && yarn start.