Add a section about common memory management patterns between wasm and JS

This would be a new reference sub-section.

Things to mention:

[ ] To help alleviate that pain, mention the JS equivalent of RAII:

function withResource(f) {
  let resource = new Resource();
  try {
      return f(resource);
  } finally {
      resource.free();
  }
}

also the async version of that, with return await f(resource);

[ ] Static globals in rust that don't need to have their lifetime managed by JS
[ ] Mention upcoming GC weakrefs, link to tracking page, explain their relevance to cleaning up objects in wasm
[ ] Mayyyybe mention how one could build reference counting in JS of dynamically allocated wasm objects? I don't know of anyone actually doing this, so maybe not mention it until then?

Anything else?

rustwasm / book