Add support for @salesforce/messageChannel imports

[lukethacoder]

Is your feature request related to a problem? Please describe.
Manually creating mocks and defining module name/path is a PITA.

"modules": [
  {
    "name": "@salesforce/messageChannel/CustomChannelOne",
    "path": "./__mocks__/@salesforce/messageChannel/CustomChannelOne.js"
  },
  {
    "name": "@salesforce/messageChannel/CustomChannelTwo",
    "path": "./__mocks__/@salesforce/messageChannel/CustomChannelTwo.js"
  }
]

Describe the solution you'd like
Instead of having to manually define messageChannel 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/messageChannel/CustomChannelTwo" and return a new LMS instance (see here)

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

[lukethacoder]

Will need to add lightning/messageService as an export in the @lwc-garden/utils package too (ref)