deno-fmt Allow imports to be customized to a single line imports

[PodaruDragos]

Hello guys, I would like to propose a new rule or to modify the existing one for lineWidth to allow imports to be preserved to a single line.

1. Proposal for new rule: as described in this PR from dprint
2. Propasal for changing existing rule as per a similar rule from eslint

   "lineWidth": [
      {
        "width": 80,
        "ignorePattern": "^import"
      }
    ]

I understand no-one wants to add new rules or configs to an opinionated formatter, but this doesn't need to be a new rule necessarily.