Set readStartTime when switching chapters in a single reader session (#7702)

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderPresenter.kt

@@ -423,6 +423,7 @@ class ReaderPresenter(
         if (selectedChapter != currentChapters.currChapter) {
             logcat { "Setting ${selectedChapter.chapter.url} as active" }
             saveReadingProgress(currentChapters.currChapter)
+            setReadStartTime()
             loadNewChapter(selectedChapter)
         }
     }