Updated resolving dependancies

By using 'npm ci' instead of 'npm install' you can significantly improve the speed of the build process

Author: markyroden

docs/spfx/toolchain/implement-ci-cd-with-azure-devops.md

@@ -45,9 +45,10 @@ Once the Build Definition has been created, the first thing you need to do is in
 
 ### Restoring dependencies
 
-Because third party dependencies are not stored in the source control, you need to restore those before starting to build the project. To do so add a `npm` task and set the command to `install`.
+Because third party dependencies are not stored in the source control, you need to restore those before starting to build the project. To do so add a `npm` task and set the Command to `custom` and the Command and arguments to `ci`.
 ![installing dependencies](../../images/azure-devops-spfx-03.png)
 
+
 ### Executing Unit Tests
 
 The SharePoint Framework does not provide a testing framework by default (since 1.8.0), we will leverage Jest with this sample. These modules will be installed in a later step and it is highly recommended at a minimum to test the business logic of your code to get feedback on any potential issues or regressions as soon as possible. To have Azure DevOps execute your unit tests, add a `npm` task. Set the `command` to `custom` and `custom command` field, enter `test`. Then set the `Working Directory` option to `$(Build.SourcesDirectory)`.