[Modlog] Send case to channel based on case type

# Feature request

#### Select the type of feature you are requesting:

- [ ] Cog
- [ ] Command
- [x] API functionality

#### Describe your requested feature

While you may want to have all case types logged, some might be more important than others and an option to split those cases in multiple channels based on case type would be great. Possibly we could create "groups" of case types, and be able to specify a channel for a group.
If we would have such groups, it could also be nice to have an option option to find cases based on those groups but that is kind of a separate feature request.