Exclude Apps from App Usage

### Please check before submitting an issue

- [x] I am using the latest version of App Manager
- [x] I have searched the issues and haven't found anything relevant
- [x] I have read the docs

### Describe a description of the new feature

I really like the concept of AppManager but I'm missing the feature to exclude Apps from App usage. I use a App called AmpereFlow which enables an always-on screen while charging. So every time i charge my phone I have like 3h extra phone usage because of this app. And I haven't found ANY foss app for android which allows you to exclude apps from usage tracking.

### Describe the solution you'd like

Add the option to exclude apps from the app usage screen.

### Describe alternatives you've considered

I searched for an other app but I only found Stayfree which is pretty good but closed source and with bad privacy. All FOSS apps of this kind are missing the feature.

### Additional context