Angular: StateService injected in custom library results in R3InjectorError

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This is a (check one box):

- [x ] Bug Report
- [ ] Feature Request
- [ ] General Query

My version of UI-Router is: (type version)
@uirouter/angular: 10.0.0
@uirouter/core: 6.0.8
@uirouter/rx: 1.0.0

# Bug Report

#### Current Behavior:
I am injecting the StateService in a component of a custom angular library I am building. As soon as I do that though, the following happens:

```
R3InjectorError(AppModule)[StateService -> StateService -> StateService]:
NullInjectorError: No provider for StateService!
```
and the whole app does not work.

#### Expected Behavior:
No error, being able to use the Service and not crashing the whole application.

#### Link to Plunker or stackblitz that reproduces the issue:
Github-Repo: https://github.com/Vortilion/angular-library-stateservice-issue