Add support for @salesforce/schema imports

[lukethacoder]

Is your feature request related to a problem? Please describe.
Manually defining schema imports for each field is a PITA.

"modules": [
  {
    "name": "@salesforce/schema/Account.Id",
    "path": "./__mocks__/@salesforce/schema/Account.Id.js"
  },
  {
    "name": "@salesforce/schema/Account.Name",
    "path": "./__mocks__/@salesforce/schema/Account.Name.js"
  }
]

Describe the solution you'd like
Instead of having to manually define schema imports, auto-calculate them as part of a custom module resolver or hook, adding to the existing @lwc-garden/utils package.

Take the import "@salesforce/schema/Account.Id" and return the text after the final / (e.g. "Account.Id"). May be worth considering namespaced packages?

Describe alternatives you've considered
Could build a script that dynamically updates the lwr.config.json modules array.