Add [Inject] to ZenjectSceneLoader Constructor

[zb-sj]

Inject Attribute is required for ConstructorChoiceStrategy.InjectAttribute

Pull request checklist

Please check if your PR fulfills the following requirements:

• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been reviewed and added / updated if needed (for bug fixes / features)
• [x] No compiler errors or warnings

Pull request type

Please check the type of change your PR introduces: - [x] Bugfix - [ ] Feature - [ ] Code style update (formatting, renaming) - [ ] Refactoring (no functional changes, no api changes) - [x] Build related changes - [ ] Documentation content changes - [ ] Other (please describe): ## Issue Number

Issue Number: N/A

What is the current behavior?

• Validation fails and won't play with Zenject.ZenjectSceneLoader

  ArgumentException: Type 'Zenject.ZenjectSceneLoader' does not have a default constructor

What is the new behavior?

• Validation passes and play as expected

Does this introduce a breaking change?

• [ ] Yes
• [x] No

Other information

• 9.3.0 UPM Environmnet

On which Unity version has this been tested?

• [x] 2020.4 LTS
• [ ] 2020.3
• [ ] 2020.2
• [ ] 2020.1
• [ ] 2019.4 LTS
• [ ] 2019.3
• [ ] 2019.2
• [ ] 2019.1
• [ ] 2018.4 LTS

Scripting backend:

• [ ] Mono
• [x] IL2CPP