Add last update time to Updates Tab (closes #5466)

Co-authored-by: datreesezcup <datreesezcup@users.noreply.github.com>

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

@@ -742,6 +742,7 @@
     <string name="updating_library">Updating library</string>
     <string name="update_already_running">An update is already running</string>
     <string name="cant_open_last_read_chapter">Unable to open last read chapter</string>
+    <string name="updates_last_update_info">Library last updated: %1$s</string>
 
     <!-- History fragment -->
     <string name="recent_manga_time">Ch. %1$s - %2$s</string>