fix: label the ringtone preview button as a preview

TalkBack read the play button as the tone's name alone, right after the
row that already said it.

app/src/main/java/de/jeanlucmakiola/clockula/ui/common/RingtonePickerScreen.kt

@@ -225,7 +225,10 @@ private fun RingtoneOptionRow(
             previewUri != null -> {
                 {
                     IconButton(onClick = { onPreview(previewUri) }) {
-                        Icon(Icons.Rounded.PlayArrow, contentDescription = title)
+                        Icon(
+                            Icons.Rounded.PlayArrow,
+                            contentDescription = stringResource(R.string.ringtone_preview_play, title),
+                        )
                     }
                 }
             }

app/src/main/res/values/strings.xml

@@ -169,6 +169,7 @@
     <string name="ringtone_silent">Silent</string>
     <string name="ringtone_silent_summary">Vibration only</string>
     <string name="ringtone_device_default">Device default alarm sound</string>
+    <string name="ringtone_preview_play">Preview %1$s</string>
     <string name="ringtone_preview_stop">Stop %1$s</string>
     <string name="ringtone_pick_file">Choose from files\u2026</string>
     <string name="ringtone_none_available">This device has no alarm sounds. Clockula will use the system default.</string>