Add support for Rush

[victordidenko]

Rush is a Microsoft's monorepo management tool https://rushjs.io

It uses own config file rush.json and monorepo packages are listed in it, like this:

  "projects": [
    {
      "packageName": "my-toolchain",
      "projectFolder": "tools/my-toolchain"
    }
  ]

there is no root package.json file, and sherif fails with an error

 ⨯ error Failed to collect packages
   `package.json` not found in "."

[QuiiBz]

Indeed, Sherif supports NPM/Yarn workspaces (via the root package.json's workspaces field) or PNPM workspace (via the pnpm-workspace.yaml file).

Supporting Rush is not an easy task. I'll leave this issue open so folks can react/comment to see if more than just a few people would use this feature.