Changes to webpack-dev-server which is compatible with webpack 5.x, adds missing typescript definition for property

What does it do?

Had issues getting development going since the project uses webpack 5.x but webpack-serve depends on 4.x.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• Updated documentation (if applicable)
• Added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• My changes generate no new warnings