Allow specifying excluded files by regular expression

[wilhelmklopp]

In snappydoo config

{
  "snappydoo": {
    "exclude": [
      "SnapshotFileName", // exclude files with exactly this filename (when `test.js.snap` is appended)
      {
        type: "regex",
        expression: "(.*)" // exclude all files that match this expression
      }
    ]
  }
}