reader/readingtime: fix incorrect package name

internal/reader/readingtime/readingtime.go

@@ -1,7 +1,7 @@
 // SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-// Package readtime provides a function to estimate the reading time of an article.
+// Package readingtime provides a function to estimate the reading time of an article.
 package readingtime
 
 import (