message: docs: update README.md
  Fix typo/spelling mistake
diff: @@ -24,7 +24,7 @@ GraphQL Playground uses components of GraphiQL under the hood but is meant as a
  - Configuration of HTTP headers
  - Tabs
  -See the following question for more additonal features.
  +See the following question for more additional features.
  ### What's the difference between the desktop app and the web version?
  