Update build-native-widget.md

[wpenris]

This explanation was unusable as the paths used got you stuck; I have improved that by first setting up a test project, and then setting up the widget in a sub folder. I have also added example paths.

Furthermore, the component select for the widget builder was missing (functional). I also made some things easier to read. It would help if this could be tested and merged. I also have a new screenshot for after the yo command, but I cannot upload files anymore; I have attached a new file/image for line 119.

Best regards,

Wouter