Examples broken on web, pulling in `env` package

## Bevy version

`main` @ `139515278c416b216610c796687c3428f528fbd2`

## \[Optional\] Relevant system information

If you cannot get Bevy to build or run on your machine, please include:

- the Rust version you're using (you can get this by running `cargo --version`)
- Bevy relies on the "latest stable release" of Rust
- nightly should generally work, but there are sometimes regressions: please let us know!
- the operating system or browser used, including its version
- e.g. Windows 10, Ubuntu 18.04, iOS 14

If your bug is rendering-related, copy the adapter info that appears when you run Bevy.

```ignore
`AdapterInfo { name: "NVIDIA GeForce RTX 2070", vendor: 4318, device: 7938, device_type: DiscreteGpu, backend: Vulkan }`
```

You should also consider testing the examples of our upstream dependencies to help isolate any setup-specific issue:

- [`wgpu`](https://github.com/gfx-rs/wgpu) for rendering problems
- [`winit`](https://github.com/rust-windowing/winit) for input and window management
- [`gilrs`](https://docs.rs/gilrs/latest/gilrs/) for gamepad inputs

## What you did

With the [Bevy CLI](https://github.com/TheBevyFlock/bevy_cli) installed, use

```sh
bevy run --example=breakout web
```

on the `bevy` repo.

## What went wrong

Loading forever due to an error, in the browser console I get:

```txt
Uncaught TypeError: The specifier “env” was a bare specifier, but was not remapped to anything. Relative module specifiers must start with “./”, “../” or “/”.
```

## Additional information

The first line of the generated JS is:

```js
import * as __wbg_star0 from 'env';
```

Which looks... wrong. Not sure where it comes from.

Note that this _could_ also be a bug related to the Bevy CLI itself, but it's unlikely as it still works with other projects.

Start by reproducing `bevy run --example=breakout web` and inspecting the generated JavaScript, especially its `import * as __wbg_star0 from 'env';` line. Trace where that bare `env` import is introduced and confirm that the web example loads successfully in the browser without the console error.

Written by the indexing model from the issue text.