Improve Angular Testing Library API documentation

I am new to Angular Testing and stumbled across some misunderstandings while writing my first tests. I would like to help you improve it, so let's start collecting the issues. 🙂

1. The example for the declarations (within RenderOptions) is wrong. It configures the providers. Furthermore there is no descriptions for the providers option. https://testing-library.com/docs/angular-testing-library/api#declarations
2. We might also add a note which of the RenderOptions are passed to the Angular TestBed. Or even separate those from the added render properties.
3. Explaining that this library still works with the core testing functionality of Angular under the hood will also help to implement non-standard situations. For example in one test I needed to interact with a service. This can be done with the Angular TestBed: TestBed.get(TargetService).init();

从链接的 RenderOptions 页面上的 Angular Testing Library API 文档开始。检查 declarations 示例，添加缺失的 providers 描述，并明确哪些选项会传递给 Angular TestBed，以及 TestBed 如何支持非标准情况。当示例和说明性注释准确涵盖这些要点时，即可视为完成。