Inconsistant asset loading path between platforms in workspaces

## Bevy version

0.5

## Operating system & version

Manjaro-21-0.2

## What you did

Example repo: https://github.com/SarthakSingh31/bevy_workspace

I tired to load assets from inside a crate in a workspace on a native build and a `wasm32-unknown-unknown` build.

## What you expected to happen

Bevy loads the assets from the same path.

## What actually happened

Bevy tries to load the assets from different paths.

On native it uses `FileAssetIo` which looks for the assets in the crate. (in the example repo it looks for `/test_workspace/test_crate/assets`)

On wasm it uses `WasmAssetIo`which looks for the crate in the execution path which in this case is the workspace path. (in the example repo it looks for `/test_workspace/assets`)

## Additional information

I think `AndroidAssetIo` might have the same issue.