How to fetch the content author name with views in twig?
Better way to answer this is through  debugging the views fields by enabling the page_array check under the devel module settings.We get each and every fields that are available for the twig template.

There are two steps to get this working 

Follow the steps mentioned in the comment: 


https://www.drupal.org/forum/support/post-installation/2011-06-26/drupal-72-views-adding-authors-name-of-a-node#comment-4919120
You have to be careful while selecting the field .Please select the
field marked in the attached image.

Then in the twig template views-view-fields--VIEWNAME.html.twig the
variable to be used is {{fields.nane.content}}


In addition to the above while researching for the variable name i found that most of the field names commonly used are available under admin/reports/fields in the backend of Drupal 8