message: choose the correct fetcher based on useragent
diff: // under the License.
  import browser from "webextension-polyfill";
  +import parser from "ua-parser-js";
  import { migrateTestCase, migrateProject } from "./legacy/migrate";
  import UiState from "../stores/view/UiState";
  import ModalState from "../stores/view/ModalState";
  import Selianize, { ParseError } from "../../selianize";
  +import chromeGetFile from "./filesystem/chrome";
  +import firefoxGetFile from "./filesystem/firefox";
  export const supportedFileFormats = ".side, text/html, application/zip";
  +const parsedUA = parser(window.navigator.userAgent);
  +
  +export function getFile(path) {
  + const browserName = parsedUA.browser.name;
  + if (browserName === "Chrome") {
  + return chromeGetFile(path);
  + } else if (browserName === "Firefox") {
  + return firefoxGetFile(path);
  + } else {
  + return Promise.reject(new Error("Operation is not supported in this browser"));
  + }
  +}
  export function saveProject(project) {
  project.version = "1.0";
  