migrate wasm example to trunk (#844)

## Description

This PR migrates the wasm example from an npm/webpack based approach to [trunk](https://trunkrs.dev/). Fixes #834.

Of note:
the `console_error_panic_hook` dependency was gated in `Cargo.toml` via `[target."cfg(debug_assertions)".dependencies]`. This is documented as nonfunctional and will throw a warning on build:
```
warning: Found `debug_assertions` in `target.'cfg(...)'.dependencies`. 
This value is not supported for selecting dependencies and will not work as expected. 
To learn more visit https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#platform-specific-dependencies
```

Since the actual usage of `console_error_panic_hook` is *also* gated in `lib.rs` behind `#[cfg(debug_assertions)]` it didn't make sense to have the cargo gate in place, hence I have removed it.

## Next steps

If this PR is merged, the [wiki page](https://github.com/RustAudio/cpal/wiki/Setting-up-a-new-CPAL-WASM-project) linked in the root README should be updated as well.

examples/wasm-beep/.gitignore

@@ -1,6 +1,3 @@
 Cargo.lock
-node_modules
 /dist
 /target
-/pkg
-/wasm-pack.log

examples/wasm-beep/Cargo.toml

@@ -18,6 +18,8 @@ lto = true
 
 [dependencies]
 cpal = { path = "../..", features = ["wasm-bindgen"] }
+# `gloo` is a utility crate which improves ergonomics over direct `web-sys` usage.
+gloo = "0.11.0"
 # The `wasm-bindgen` crate provides the bare minimum functionality needed
 # to interact with JavaScript.
 wasm-bindgen = "0.2.45"
@@ -27,15 +29,12 @@ wasm-bindgen = "0.2.45"
 # allocator, so it's not enabled by default.
 wee_alloc = { version = "0.4.2", optional = true }
 
+# The `console_error_panic_hook` crate provides better debugging of panics by
+# logging them with `console.error`.
+console_error_panic_hook = "0.1.5"
+
 # The `web-sys` crate allows you to interact with the various browser APIs,
 # like the DOM.
 [dependencies.web-sys]
 version = "0.3.22"
-features = ["console"]
-
-# The `console_error_panic_hook` crate provides better debugging of panics by
-# logging them with `console.error`. This is great for development, but requires
-# all the `std::fmt` and `std::panicking` infrastructure, so it's only enabled
-# in debug mode.
-[target."cfg(debug_assertions)".dependencies]
-console_error_panic_hook = "0.1.5"
+features = ["console", "MouseEvent"]

examples/wasm-beep/README.md

@@ -1,29 +1,28 @@
 ## How to install
 
+[trunk](https://trunkrs.dev/) is used to build and serve the example.
 ```sh
-npm install
+cargo install --locked trunk
+# -- or --
+cargo binstall trunk
 ```
 
 ## How to run in debug mode
 
 ```sh
 # Builds the project and opens it in a new browser tab. Auto-reloads when the project changes.
-npm start
+trunk serve --open
 ```
 
 ## How to build in release mode
 
 ```sh
-# Builds the project and places it into the `dist` folder.
-npm run build
+# Builds the project in release mode and places it into the `dist` folder.
+trunk build --release
 ```
 
 ## What does each file do?
 
 * `Cargo.toml` contains the standard Rust metadata. You put your Rust dependencies in here. You must change this file with your details (name, description, version, authors, categories)
 
-* `package.json` contains the standard npm metadata. You put your JavaScript dependencies in here. You must change this file with your details (author, name, version)
-
-* `webpack.config.js` contains the Webpack configuration. You shouldn't need to change this, unless you have very special needs.
-
 * The `src` folder contains your Rust code.