Ensure we pick the right gpu card in the example backend

[arjo129]

Connections
#6522

Description
This is my first time contributing to this project, so it may be that I'm doing something wrong. Essentially, we retain the old behavior if we use the environment variable to select our gpu. Otherwise we first try to match required features prior to selecting an adapter.

Testing

Just run the example as done before.

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy. If applicable, add:
  • --target wasm32-unknown-unknown
  • --target wasm32-unknown-emscripten
• Run cargo xtask test to run tests.
• Add change to CHANGELOG.md. See simple instructions inside file.