Add generic support for [@types/koa-mount]  (#36365)
Add generic support for [@types/koa-mount]  (#36365)

* Add generic support

* fix: lint errors

* fix: unnecessary semicolon

* feat: add generic types in overload

dsebastien/DefinitelyTyped,georgemarshall/DefinitelyTyped,markogresak/DefinitelyTyped,georgemarshall/DefinitelyTyped,dsebastien/DefinitelyTyped,georgemarshall/DefinitelyTyped,georgemarshall/DefinitelyTyped,mcliment/DefinitelyTyped