Switch to prettier for formatting

[lilleyse]

• Follows the same conventions as CesiumJS.
• Doesn't actually run the formatter or install the pre-commit hook yet.
• The changes can be viewed here: https://github.com/CesiumGS/obj2gltf/compare/prettier-test?expand=1

Steps for migrating to prettier will be as follows:

1. Merge this into main
2. Add a pre-prettier tag
3. Actually run prettier and commit the code changes to main
4. Add a post-prettier tag
5. Open a follow-up PR to add the pre-commit hooks for running prettier

Recommendations for how to update your branches can be found here: https://community.cesium.com/t/cesiumjs-source-code-is-now-formatted-with-prettier/9362