Korean letters are not typed properly in markdown widget fields

[DaleSeo]

- Do you want to request a feature or report a bug?
bug

- What is the current behavior?
Korean letters are not typed properly in markdown widget fields. Letter disappear when the editor UI blinks. This issue doesn't occur with either string widget or text widget.

- If the current behavior is a bug, please provide the steps to reproduce.
Just try to type any Korean letters in a markdown widget field.

- What is the expected behavior?
Korean letters are expected to be entered properly in markdown widget fields without losing any letters.

- Please mention your versions where applicable.

Netlify CMS version: 2.0.6
Browser version: Chrome 67.0.3396.99

Node.JS version: v8.11.3
Operating System: Windows

- Please link or paste your config.yml below if applicable.

backend:
  name: git-gateway
  branch: master # Branch to update (optional; defaults to master)

# This line should *not* be indented
publish_mode: editorial_workflow

# This line should *not* be indented
media_folder: "source/images/uploads" # Media files will be stored in the repo under images/uploads
public_folder: "/images/uploads" # The src attribute for uploaded media will begin with /images/uploads

collections:
  - name: "posts" # Used in routes, e.g., /admin/collections/blog
    label: "Post" # Used in the UI
    folder: "source/_posts" # The path to the folder where the documents are stored
    create: true # Allow users to create new documents in this collection
    slug: "{{slug}}" # Filename template, e.g., YYYY-MM-DD-title.md
    fields: # The fields for each document, usually in front matter
      - {label: "Title", name: "title", widget: "string"}
      - {label: "Publish Date", name: "date", widget: "datetime"}
      - {label: "Categories", name: "categories", widget: "select", options: ['Java', 'JavaScript', 'Python']}
      - {label: "Tags", name: "tags", widget: "list"}
      - {label: "Body", name: "body", widget: "markdown"}

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[erezrokah]

Duplicate of #1347