Please update libraries to AndroidX and latest Google GMS versions

[RoarGronmo]

In writing time this is now at least:

app gradle:

androidx.appcompat:appcompat:1.1.0
androidx.cardview:cardview:1.0.0
androidx.recyclerview:recyclerview:1.1.0
androidx.legacy:legacy-support-v4:1.0.0
com.google.firebase:firebase-ads:18.3.0

This implies also changes to AndroidManifest.xml

in project gradle:

classpath 'com.google.gms:google-services:4.3.3'

[galcyurio]

This sample project seems to need library upgrade.
And also migrate to AndroidX.
I can migrating this and send a PR.

However, this codelab documentation also needs to change.
How about this?