book: Add section about wasm2asm fallback to support IE11 and older browsers that don't have WebAssembly

[fitzgen]

The wasm2asm tool in binaryen (soon to be renamed wasm2js) is a near feature complete solution for compiling wasm into JS so that you can support IE11 and older browsers that don't have support for WebAssembly.

We should add a section to the book about how to make this work, since it is a pretty common need.

[adityac8]

Hey, @fitzgen I would like to work on this issue 😄

[Hywan]

@adityac8 If you would like a usage example, check https://github.com/Hywan/gutenberg-parser-rs/blob/e28f1859ee9c274cc8cb2001ebe6b2f31cdda59f/justfile#L36-L44. It explains how to compile it and make it work in IE 11. For the complete usage, see https://github.com/Hywan/gutenberg-parser-rs/tree/master/bindings/asmjs. If you need any help, ping me :-).

[adityac8]

Thank you @Hywan I'll go through the files. If I don't understand something, I'll ping you. Can I know your IRC? 😸

[jrichocean]

This Issue can now be found at here