Importing a folder (expect to import "index") doesn't work, index must be explicit

Hello,

Related to the previous issue https://github.com/godotjs/GodotJS/issues/52

I also noticed that if for example you have a folder structure like this: `mystuff/index.ts`

You are expecting to importing as follows `import things from './mystuff'`

But it doesn't work and needs the index to be added

This one is quite easy to test on the Examples projects