Please fill in this template.

• Use a meaningful title for the pull request. Include the name of the package modified.
• Test the change in your own code. (Compile and run.)
• Follow the advice from the readme.
• Avoid common mistakes.
• Run npm run lint package-name (or tsc if no tslint.json is present).

If changing an existing definition:

• Provide a URL to documentation or source code which provides context for the suggested changes: Updated webpack-dev-middleware to v2 #22267
• Increase the version number in the header if appropriate.
• If you are making substantial changes, consider adding a tslint.json containing { "extends": "dtslint/dt.json" }.

Sadly there was a bug in the CI (#22267 (comment)) which didn't catch the errors of my incorrect pull request to include webpack-dev-middleware v2 changes (#22267). This PR tries to fix my older PR.

(Note: First time I created a new major version for lib here. Hope I checked everything.)