Describe the feature you'd like to request

As a user, I want to be able to cache tasks defined in the root package.json and cache them.

{
   "pipeline": {
      "_root#build": {
          "inputs": ["list/of/inputs/to/hash/**"],
          "outputs": ["some/output/dir/**"],
          "dependsOn":["prepare"]
      },
      "_root#prepare": {
          "inputs": ["foo/**"],
          "outputs": ["another/output/dir/**"],
      },
      ....
}      

Describe the solution you'd like

• Ability to specify inputs to task #523
  • Consider migrating env vars to inputs and out of dependsOn? idk?
• Update task graph construction to include root task edges in scheduler https://github.com/vercel/turborepo/blob/main/cli/internal/core/scheduler.go#L183
  • We may also need to adjust resolving root deps, perhaps we can simply add the root to PackageInfos and clean up specialized lockfile resolution https://github.com/vercel/turborepo/blob/main/cli/internal/context/context.go#L164

Describe alternatives you've considered

None