Use some animations in sheet toolbar

app/src/main/java/org/koitharu/kotatsu/base/ui/widgets/AnimatedToolbar.kt

@@ -0,0 +1,22 @@
+package org.koitharu.kotatsu.base.ui.widgets
+
+import android.content.Context
+import android.graphics.drawable.Drawable
+import android.util.AttributeSet
+import android.view.View
+import androidx.appcompat.widget.Toolbar
+import androidx.core.view.isGone
+import com.google.android.material.appbar.MaterialToolbar
+
+class AnimatedToolbar(context: Context, attrs: AttributeSet?) : MaterialToolbar(context, attrs) {
+	companion object {
+		private val navButtonViewField = Toolbar::class.java.getDeclaredField("mNavButtonView")
+			.also { it.isAccessible = true }
+	}
+
+	override fun setNavigationIcon(icon: Drawable?) {
+		super.setNavigationIcon(icon)
+
+		(navButtonViewField.get(this) as? View)?.isGone = (icon == null)
+	}
+}