Steps to reproduce the issue

i need add 2 fields to the component content (articles), need add 2 images and try some examples but don't work :-( have a github with the last try

https://github.com/javimata/plg_addfield

Can help me to check what happend? what i do wrong?

Expected result

View 2 fields new in the component

Actual result

I don't see the fields

System information (as much as possible)

Nothing

Additional comments

I try the example in the official documentation and i use it but dont work