Document dev server overlay improvement

[malcolm-kee]

Feature to document

There are new dev server overlay configurations with the following changes:

• feat: catch runtime error webpack-dev-server#4605
• feat: allow filter overlay message with function webpack-dev-server#4813

Author(s)

@malcolm-kee

Additional information

• I am willing to work on this issue and submit a pull request.

I plan to work on this next week, but happy to let others work on this if they're interested.

[chenxsan]

Closed via #6809