[FEATURE REQUEST] Let us know that a new version is available even without auto-update enabled

### Please confirm these before moving forward.

- [x] I have searched for my feature proposal and have not found a work-in-progress/duplicate/resolved/discarded issue.
- [x] This proposal is a completely new feature. If you want to suggest an improvement or an enhancement, please use [this template](https://github.com/marticliment/WingetUI/issues/new?assignees=marticliment&labels=enhancement&projects=&template=enhancement-improvement.yml&title=%5BENHANCEMENT%5D+%28Enter+your+description+here%29).

### Describe the new feature

I'm really pleased that we now have the option to disable UniGetUI's automatic updates while still being able to check for updates manually. It would also be great to have a checkbox similar to the existing 'Update UniGetUI automatically,' but instead labeled something like 'Check for updates even if automatic updates are disabled.' This would notify us when a new UniGetUI update is available without automatically initiating the update.

### Describe how this new feature could help users

I'm a bit of a control freak, so I've disabled automatic updates for UniGetUI on all my machines and servers. However, I occasionally forget to update UniGetUI on one of them. With this feature, UniGetUI would at least notify me when a new version is available, allowing me to update it manually.