Feature: Allow defining targets per pattern or group

### Prerequisites

- [X] I have written a descriptive issue title
- [X] I have searched existing issues to ensure the feature has not already been requested

### 🚀 Feature Proposal

It would be very useful to be able to define target levels per pattern or group.

Not matching ones would use default target.

### Motivation

For certain dependencies we know that it's safe to automerge majors and for some other dependencies it's not.

### Example

```
target: minor
custom-targets:
- target: major
patterns:
- "@foo*"
groups:
- "dev-dependencies"
```