DOC Add composer install command and repository link

Author: emteknetnz

docs/en/index.md

@@ -6,8 +6,6 @@ icon: link
 
 # Linkfield
 
-Make sure that your Silverstripe CMS installation has [`silverstripe/linkfield`](https://github.com/silverstripe/silverstripe-linkfield/) installed.
-
 This module provides a Link model and CMS interface for managing different types of links. Including:
 
 - Emails
@@ -16,4 +14,14 @@ This module provides a Link model and CMS interface for managing different types
 - Links to assets within the CMS
 - Phone numbers
 
+## Installation
+
+```bash
+composer require silverstripe/linkfield
+```
+
+## GitHub repository
+
+<https://github.com/silverstripe/silverstripe-linkfield>
+
 [CHILDREN includeFolders]