Adds rust-wasm-starter

[kvendrik]

Add rust-wasm-starter which provides a starter template to get started with Rust and WebAssembly in seconds. Includes handy dev features to start coding Rust right away with minimal overhead like auto-complication on file save and live reloading.

• [x] I've read CONTRIBUTING.md.
• [x] Description explains the issue / use-case resolved, and auto-closes the related issue(s) (https://help.github.com/articles/closing-issues-via-commit-messages/).

cc @mbasso