Importing nested files causes dependency error

When importing a repository from github, I have two issues that have been troubling:

### DevDependencies are not imported

When the package.json file is imported, it's clearing everything except for the dependencies entry. This causes problems when importing a project that uses dev dependencies. My particular case is usually for a project that includes tests and requires `react-test-renderer` as a devDependency. When imported the project complains that this dependency is missing. I don't want this to be installed as a regular dependency.

### Importing nested files causes dependency error

When importing from somewhere other than the root of a package, snack complains that the dependency is missing and prompts to install a dependency that includes the nested folder structure. If you do this, snack works, but the project fails locally because that package does not exist in npm (405 error).

For example:
```Add react-native-vector-icons/MaterialIcons to package.json?```
```Add @react-native-community/async-storage/jest/async-storage-mock to package.json?```

Start by reproducing the GitHub import with a package.json containing devDependencies and imports such as react-native-vector-icons/MaterialIcons or @react-native-community/async-storage/jest/async-storage-mock. Trace the dependency extraction and install prompt for nested imports; done means devDependencies are preserved and nested paths resolve to their owning packages without suggesting nonexistent npm packages.

Written by the indexing model from the issue text.