Add a full project folder when adding appinfo.json

- Split from https://github.com/ArcGIS/appstudio-vscode/issues/42
- launch an appinfo.json from visual studio code > file > open file > choose an appinfo.json file, if there isn't a project open already, the whole project is opened (this is good). but, if there is already a project open, i only get the appinfo.json opened. we should get the whole project added.