[Feature] Notification when a page change has NOT changed in x amount

expanding on #4

when a page hasnt been updated in x amount to make a notification.

example i have cron job do action. if no file changed in 1 day there is problem. send alert!

Read the related issue #4 and compare its existing page-change behavior with this request. Investigate how the cron job and notification flow represent a page that has not changed, then define the configurable time threshold and alert behavior; done means an unchanged page triggers the expected notification after that interval.

Written by the indexing model from the issue text.