🚀 Announcements: Dynamic colour changing/countdown feature

### Workspace

announcements

### 🔖 Feature description

Add a colour changing feature or countdown feature, to highlight and make visible important announcements to users

### 🎤 Context

We often have alerts and maintenance schedules broadcasted on out announcement plugin, to make our users aware of these things.
We would like to know if its possible to make the banner change colour the closer to the due date it gets
Blue - initial announcement/4-5 days before due date
Yellow/Orange - 3 days before due date
Red - 1-2 days before due date
Possible for Green if the same announcement is active and due date is passed (unsure if the banner disappears as we always seem to have a new one active)

This might also be case for these type of banners to always be present as they match this topic (maintenance/releases). So these are always present while other banners can be placed under and be dismissed

### ✌️ Possible Implementation

Add a new banner that cannot be dismissed that highlights a specific type of topic, in this case release/maintenance. The colour of the banner changes the closer to the due date it gets to

### 👀 Have you spent some time to check if this feature request has been raised before?

- [x] I checked and didn't find similar issue

### 🏢 Have you read the Code of Conduct?

- [x] I have read the [Code of Conduct](https://github.com/backstage/community-plugins/blob/main/CODE_OF_CONDUCT.md)

### Are you willing to submit PR?

No, but I'm happy to collaborate on a PR with someone else