Merge branch 'repository-files-doc' into 'master'

Add examples to repository files API

## What does this MR do?

Add examples to repository files API.

## Why was this MR needed?

There were no examples.

## What are the relevant issue numbers?

fixes #19779


See merge request !5465

doc/api/repository_files.md

@@ -12,6 +12,10 @@ Allows you to receive information about file in repository like name, size, cont
 GET /projects/:id/repository/files
 ```
 
+```bash
+curl -X GET -H 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' 'https://gitlab.example.com/api/v3/projects/13083/repository/files?file_path=app/models/key.rb&ref=master'
+```
+
 Example response:
 
 ```json
@@ -39,6 +43,10 @@ Parameters:
 POST /projects/:id/repository/files
 ```
 
+```bash
+curl -X POST -H 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' 'https://gitlab.example.com/api/v3/projects/13083/repository/files?file_path=app/project.rb&branch_name=master&content=some%20content&commit_message=create%20a%20new%20file'
+```
+
 Example response:
 
 ```json
@@ -62,6 +70,10 @@ Parameters:
 PUT /projects/:id/repository/files
 ```
 
+```bash
+curl -X PUT -H 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' 'https://gitlab.example.com/api/v3/projects/13083/repository/files?file_path=app/project.rb&branch_name=master&content=some%20other%20content&commit_message=update%20file'
+```
+
 Example response:
 
 ```json
@@ -94,6 +106,10 @@ Currently gitlab-shell has a boolean return code, preventing GitLab from specify
 DELETE /projects/:id/repository/files
 ```
 
+```bash
+curl -X PUT -H 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' 'https://gitlab.example.com/api/v3/projects/13083/repository/files?file_path=app/project.rb&branch_name=master&commit_message=delete%20file'
+```
+
 Example response:
 
 ```json