fix typescript cannot infer from mappedState

[hanyf]

Hello, I encountered some problem when using this package, and tried to resolve it. hope it helps.

1. fix a problem of typescript inferring from mappedState

 const mappedState = mapState({
    loading: () => {},
    ...
 });

mappedStgate.loading()
             ^^^^^^ --> Property loading does not exist on type unknown

2. fix a problem when build typescript d.ts when this project under parent's node_moudes, which not generates all d.ts.

[alexander-heimbuch]

Thanks a lot!