Option to provide notifications for images that haven't been updated in X days

[zacps]

Is your feature request related to a problem? Please describe.

I run some images for applications from random people in the community. Some of these images are no longer maintained.

This can have security implications if they haven't received necessary updates.

Describe the solution you'd like

I would like to be able to configure watchtower to send a notification if an image has not been updated in X days, for example I would probably set this to about a year. This way I can identify images which are no longer maintained and swap them out for alternatives.

Describe alternatives you've considered

This could be a standalone application, but watchtower already checks for image updates and can send notifications, so it seems a sensible place to do it.

Additional context

No response

[github-actions[bot]]

Hi there! 👋🏼 As you're new to this repo, we'd like to suggest that you read our code of conduct as well as our contribution guidelines. Thanks a bunch for opening your first issue! 🙏

[simskij]

This sounds like a really nifty feature to have. Would you be interested in having a stab at it? I'm happy to assist with code reviews and such.

[zacps]

Absolutely! I'm planning on setting some time aside for open source contributions for Hacktoberfest, so I'll try to get to it then :).