[Suggestion] Add to comic info page, when the last strip was successfully extracted

[Olf0]

Add as a last line above the example picture to the comic info page, when the last strip (i.e. the one cached) was successfully extracted. This will make it easier to determine if a comic is dead or extractions fails due to website changes.

NB: This time-stamp is likely already captured to compare the cached strip with the current strip online (to check if it is newer and hence ought to be downloaded), just not displayed.