Add Logging on background redeemer (#3545)

Author: Knight1

ArchiSteamFarm/Localization/Strings.resx

@@ -807,4 +807,7 @@ Process uptime: {1}</value>
 		<value>Decryption of {0} database component has failed. This can be OK if you've just changed your bot's {1}, you should no longer observe this warning on the next run then. Otherwise, you should investigate and find out the exact reason for failure.</value>
 		<comment>{0} will be replaced by bot database component's name (string), {1} will be replaced by bot config component's name (string).</comment>
 	</data>
+	<data name="WarningNoValidKeysFound" xml:space="preserve">
+		<value>No valid keys were found in your .keys file for redemption. Please ensure your keys are in the correct format.</value>
+	</data>
 </root>

ArchiSteamFarm/Steam/Bot.cs

@@ -1495,7 +1495,11 @@ internal async Task ImportKeysToRedeem(string filePath) {
 
 				if (gamesToRedeemInBackground.Count > 0) {
 					AddGamesToRedeemInBackground(gamesToRedeemInBackground);
+				} else {
+					ArchiLogger.LogGenericWarning(Strings.WarningNoValidKeysFound);
 				}
+			} else {
+				ArchiLogger.LogGenericError(Strings.FormatErrorIsEmpty(filePath));
 			}
 
 			File.Delete(filePath);