如何手动获取Service实例？

某些情况下我们可能需要手动获取某Service的实例而不是通过hooks，可以使用container底层api：

import { Injectable, container, Service, Singleton } from 'service-x'

@Injectable()
class DemoService extends Service<number> {
    defaultState: number = 0
}

// get the instance of DemoService with scope Singleton
const service = container.resolveInScope(DemoService, Singleton)

console.log(service.getState()) // 0