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.
The "minimal" (wasm-bindgen only) example has been removed. It's easy enough to start with one of the framework examples and remove it if truly desired.
A new framework seed as been added as an example.
The stdweb example has been freshened up:
- It actually runs now.
- Use #[wasm_bindgen(start)] to remove the app loader script
- Don't use innerHTML, just set the text content directly.
The yew example has been freshened up:
- All the changes that were made to stdweb; actually runs, removed app loader
- Uses an ever-so-slightly more realistic counter example.

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