[zanata/zanata-platform] df20ff: Update TypeScript to 2.8.1

[GitHub]

  Branch: refs/heads/typescript-2.8
  Home:   https://github.com/zanata/zanata-platform
  Commit: df20ff6d28dead3fc5657c88142150de7b404a50
      https://github.com/zanata/zanata-platform/commit/df20ff6d28dead3fc5657c88142150de7b404a50
  Author: Sean Flanigan <sflaniga at redhat.com>
  Date:   2018-04-03 (Tue, 03 Apr 2018)

  Changed paths:
    M server/zanata-frontend/src/package.json
    M server/zanata-frontend/src/yarn.lock

  Log Message:
  -----------
  Update TypeScript to 2.8.1