Improve packages API documentation based on review

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

doc/api/README.md

@@ -48,6 +48,7 @@ The following API resources are available:
 - [Namespaces](namespaces.md)
 - [Notes](notes.md) (comments)
 - [Notification settings](notification_settings.md)
+- [Packages](packages.md) **[PREMIUM]**
 - [Pages domains](pages_domains.md)
 - [Pipelines](pipelines.md)
 - [Pipeline schedules](pipeline_schedules.md)
@@ -65,7 +66,6 @@ The following API resources are available:
   - [Project templates](project_templates.md) (see also [Templates API Resources](#templates-api-resources))
 - [Protected branches](protected_branches.md)
 - [Protected tags](protected_tags.md)
-- [Packages](packages.md) **[PREMIUM]**
 - [Repositories](repositories.md)
 - [Repository files](repository_files.md)
 - [Repository submodules](repository_submodules.md)

doc/api/packages.md

-# Packages API
+# Packages API **[PREMIUM]**
+
+This is the API docs of [GitLab Packages](../administration/packages.md).
 
 ## List project packages
 
-> [Introduced][ee-9259] in GitLab 11.8.
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/9259) in GitLab 11.8.
 
 Get a list of project packages. Both Maven and NPM packages are included in results.
 When accessed without authentication, only packages of public projects are returned.
@@ -13,7 +15,7 @@ GET /projects/:id/packages
 
 | Attribute | Type | Required | Description |
 | --------- | ---- | -------- | ----------- |
-| `id`      | integer/string | yes | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user |
+| `id`      | integer/string | yes | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user. |
 
 ```bash
 curl --header "PRIVATE-TOKEN: <your_access_token>" https://gitlab.example.com/api/v4/projects/:id/packages
@@ -38,12 +40,4 @@ Example response:
 ]
 ```
 
-By default, `GET` request return 20 results at a time because the API results
-are paginated.
-
-Read more on [pagination](README.md#pagination).
-
-This API is for listing project packages. For how to upload or install 
-Maven or NPM packages please visit [Packages](../administration/packages.md) documentation.
-
-[ee-9259]: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/9259
+By default, the `GET` request will return 20 results, since the API is [paginated](README.md#pagination).