Update docs. (#28)

Adapted from:
- https://www.amazeelabs.com/en/blog/graphql-drupalers-part-4-fetching-entities
- https://www.amazeelabs.com/en/blog/drupal-graphql-batteries-included

Author: Maria Comas

README.md

@@ -4,6 +4,22 @@
 [![Code Coverage](https://img.shields.io/codecov/c/github/drupal-graphql/graphql-views.svg)](https://codecov.io/gh/drupal-graphql/graphql-views)
 [![Code Quality](https://img.shields.io/scrutinizer/g/drupal-graphql/graphql-views.svg)](https://scrutinizer-ci.com/g/drupal-graphql/graphql-views/?branch=8.x-1.x)
 
-Please refer to the main [Drupal GraphQL] module for further information.
-
 [Drupal GraphQL]: https://github.com/drupal-graphql/graphql
+
+With `graphql_views` enabled a `GraphQL` views display can be added to any view in the system.
+
+Results can be sorted, filtered based on content fields, and relationships can be added. There is also the option to return either the full entities, just a selection of fields, or even search results taken straight from a search server.
+
+Any `GraphQL` views display will provide a field that will adapt to the views configuration:
+
+- The fields name will be composed of the views and displays machine names or configured manually.
+- If the view is configured with pagination, the field will accept pager arguments and return the result list and count field instead of the entity list directly.
+- Any exposed filters will be added to the `filters` input type that can be used to pass filter values into the view.
+- Any contextual filters will be added to the `contextual_filters` input type.
+- If a contextual filters validation criteria match an existing GraphQL type, the field will be added to this type too, and the value will be populated from the current result context.
+    
+Read more on:
+- https://www.amazeelabs.com/en/blog/graphql-drupalers-part-4-fetching-entities
+- https://www.amazeelabs.com/en/blog/drupal-graphql-batteries-included
+
+Please also refer to the main [Drupal GraphQL] module for further information.