function createDtWithFiles(files = []) {
  return {
    dataTransfer: {
      files,
      items: files.map((file) => ({
        kind: "file",
        size: file.size,
        type: file.type,
        getAsFile: () => file,
      })),
      types: ["Files"],
    },
  };
}
createDtWithFiles creates a mock data transfer object that can be used for drop events
@param {File[]} files