Warn about end of life

[danirabbit]

Problem

There’s no indication in the operating system about when it will reach end of life

Proposal

We should show a big scary warning message when we’re getting close to end of life and an even bigger scarier one when we’ve reached end of life. It should explain that elementary OS will stop receiving security and stability updates on such and such date and it will no longer be safe to use when connected to the internet and that the solution is to upgrade to the latest release

Prior Art (Optional)

No response