pr review state for each files #130

That checkbox for each files in GH PR review page. Implementation wise, these information will be attached to the review comment.

something like this:

{
  "$type": "sh.tangled.comment",
  "body": {
    "$type": "sh.tangled.markup#markdown",
    "content": "lgtm",
  },
  //...
  "review": {
    "files": [
      { "path": "/appview/state/knotstream.go", "state": "approved" },
      { "path": "/knotserver/db/events.go", "state": "need fix" },
    ]
  }
}