Consider advising users not to use Trunk for wasm builds, or warn them about some caveats

[rparrett]

It seems like people love using trunk, but there are a number of ways using trunk can bite you. I totally agree with the decision to not give full blown instructions for a tool that you don't use / aren't familiar with. So I'm not totally sure what the right thing to do in the cheatbook is.

I've collected what I know about trunk (I am also not a trunk user) based on trying to help bevy users use it. I'll toss that information down below.

• Trunk's dev web server is meant for SPAs, but bevy's asset server needs the web server to serve 404s for missing assets. By default when there is a missing file, trunk just serves 200 with the contents of index.html as the response body.

  It's a bit hard to follow what has been going on with trunk with regard to this issue. There are a number of old GH issues. There was a fork trunk-ng that added a --no-spa flag. That fork was seemingly "unforked", but I don't think that the option has made it into a release yet?

• The html file produced uses absolute paths to reference js/wasm files. This assumes the project is being placed on its own server at the web root. That might be true in a lot of cases, but it creates a great deal of confusion when deploying to itch. On itch, your project is in a subdirectory and the CDN serves missing files as 403 errors.

  I am not sure if there is a workaround for this, other than manually editing the produced html to use ./ instead of /.

• The asset folder must be configured with copy-dir.