Add contributions on a per-subdirectory basis to better describe monorepo package maintainers

**Is your feature request related to a problem? Please describe.**

The [Carbon Design System](https://github.com/carbon-design-system) primarily uses monorepos, where each repo includes multiple packages. We're looking to recognize contribution in general, but also specify maintainers on a per-package basis.

**Describe the solution you'd like**

When using the `maintenance` key (or any key for that matter), be able to specify if that key is specific to a subdirectory of the repo. For example, maybe something like this:

```json
{
"projectName": "carbon",
"projectOwner": "carbon-design-system",
"repoType": "github",
"repoHost": "https://github.com",
"contributors": [
{
"login": "username",
"name": "User Name",
"profile": "https://github.com/username",
"contributions": [
"code",
"doc",
"infra",
"review",
"maintenance"
]
}
]
}
```

Could be more specific like:

```json
{
"projectName": "carbon",
"projectOwner": "carbon-design-system",
"repoType": "github",
"repoHost": "https://github.com",
"contributors": [
{
"login": "username",
"name": "User Name",
"profile": "https://github.com/username",
"contributions": [
"code",
"doc",
"infra",
"review",
{
"key": "maintenance",
"subDirectories": [
"packages/react",
"packages/styles"
]
}
]
}
]
}
```

**Describe alternatives you've considered**

1. List GitHub teams / users in [CODEOWNERS](https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners) file and then write a custom solution to use GitHub APIs to fetch team members and user information to determine maintainers on a package basis.
2. Manually list names of maintainers in READMEs in each package's folder.