The previous signature was not compatible with EventEmitter.emit(). The typescript compilation threw:
```
node_modules/socket.io/dist/namespace.d.ts(89,5): error TS2416: Property 'emit' in type 'Namespace' is not assignable to the same property in base type 'EventEmitter'.
Type '(ev: string, ...args: any[]) => Namespace' is not assignable to type '(event: string | symbol, ...args: any[]) => boolean'.
Type 'Namespace' is not assignable to type 'boolean'.
node_modules/socket.io/dist/socket.d.ts(84,5): error TS2416: Property 'emit' in type 'Socket' is not assignable to the same property in base type 'EventEmitter'.
Type '(ev: string, ...args: any[]) => this' is not assignable to type '(event: string | symbol, ...args: any[]) => boolean'.
Type 'this' is not assignable to type 'boolean'.
Type 'Socket' is not assignable to type 'boolean'.
```
Note: the emit calls cannot be chained anymore:
```js
socket.emit("hello").emit("world"); // will not work anymore
```
