show snackbar (using anko view extension)

SnackbarAnko.kt

 // Observe snackbar event
        sleepTrackerViewModel.showSnackBarEvent.observe(this, Observer {
            binding.clearButton.snackbar(it)
        })

//Anko
    implementation "org.jetbrains.anko:anko-commons:$version_anko"
    implementation "org.jetbrains.anko:anko-design:$version_anko" // For SnackBars


//  sample
https://github.com/alexshr/andfun-kotlin-sleep-tracker/blob/master/app/src/main/java/com/example/android/trackmysleepquality/sleeptracker/SleepTrackerFragment.kt