Crystal support
This [dockerfile builds a 53k do-nothing wasm file](https://github.com/tjpalmer/wasm4-docker/blob/1839d177d10642ce37a0a9e53fa5a00e6f35d9bc/cr/Containerfile) using Crystal and wasm-ld and friends, so it might be possible to support Crystal in wasm4.

Here are the todo items in case this works out:

* [ ]  `w4 new`: Add new project template
* [ ]  `w4 watch`: Add new filename suffix + build/run support
* [ ]  `w4 png2src`: Add new language parameter
* [ ]  Website: Setup documentation
* [ ]  Website: Translated code snippets for all guide pages
* [ ]  Website: Add code to Snake tutorial