firebasex addDocumentToFirestoreCollection not returning document Id

[aalshberi]

I'm submitting a ... (check one with "x")
[x] bug report
[ ] feature request
[ ] support request => Please do not submit support requests here, use one of these channels: https://forum.ionicframework.com/ or https://ionicworldwide.herokuapp.com/

Current behavior:
FirebaseX.addDocumentToFirestoreCollection() success function doesn't return the document Id.

Expected behavior:
FirebaseX.addDocumentToFirestoreCollection() success function returns the document Id

Steps to reproduce:
Try to add document to Firestore from the app using this code:
FirebaseX.addDocumentToFirestoreCollection(doc,"users",(docId)=>{
console.log(docId);
},(error)=>{
console.error(error);
})
Then in cmd :
ionic cordova build android --prod
will result in:
Argument of type '(docId: any) => void' is not assignable to parameter of type '() => void'.

If I changed the success callback in the index.d.ts file to "success: (id:string)" instead of "success: ()" the build succeeds.

Related code:
in the steps to produce section.

Ionic info::

Ionic:

Ionic CLI : 6.3.0
Ionic Framework : @ionic/angular 5.0.5
@angular-devkit/build-angular : 0.803.25
@angular-devkit/schematics : 8.3.25
@angular/cli : 8.3.8
@ionic/angular-toolkit : 2.2.0

Cordova:

Cordova CLI : 9.0.0 (cordova-lib@9.0.1)
Cordova Platforms : not available
Cordova Plugins : not available

Utility:

cordova-res (update available: 0.12.1) : 0.8.0
native-run (update available: 1.0.0) : 0.2.8

System:

Android SDK Tools : 26.1.1
NodeJS : v10.16.3
npm : 6.11.3
OS : Windows 10

[aalshberi]

Created a PR for it:
#3386