Patch-level changes

• Update types to match in-code definitions in https://github.com/winstonjs/winston/pull/2157; thanks to new contributor @flappyBug

Dependency updates by @dependabot + CI autotesting

• Bump logform from 2.4.0 to 2.4.1 in https://github.com/winstonjs/winston/pull/2156
• Bump async from 3.2.3 to 3.2.4 in https://github.com/winstonjs/winston/pull/2147

Full Changelog: https://github.com/winstonjs/winston/compare/v3.8.0...v3.8.1