save option while installing Office JavaScript SDK

Included --save option to enable NPM to include the packages to dependencies section of the package.json file.

Author: nanddeepn

docs/spfx/office-addins-create.md

@@ -44,7 +44,7 @@ You will need to deploy the solution to tenant using the **tenant scoped deploym
 Before you can use the Office JavaScript SDK in your code, you'll need to include correct types for the solution. You can install latest types by adding `@types/office-js` package from the npm to your solution with following command:
 
 ```shell
-npm install @types/office-js
+npm install @types/office-js --save
 ```
 
 You can detect if the web part is on the Office context by using page context as shown on the following property, which refers to the Office JavaScript SDK. This property value is dependent on the context where the code is being executed.
@@ -115,4 +115,4 @@ You can deploy your solution to Outlook Web App by using so called side-loading
    1. Name can be adjusted in the manifest file as needed
 
 > [!IMPORTANT]
-> Deployment process will include different steps when additional applications and desktop will be supported.
+> Deployment process will include different steps when additional applications and desktop will be supported.