Missing Effect import in examples

It seems like all the examples have
```
main :: Effect Unit
```
but are missing the import for the `Effect` type
```
import Effect (Effect)
```
<img width="1440" alt="image" src="https://user-images.githubusercontent.com/26548438/180114360-481ec320-2671-4fb4-af4d-e381fc6e3c57.png">