Added powershellgallery info

Author: alan-null

README.md

@@ -1,3 +1,18 @@
 # Crypto.AES
 
-This is a PowerShell module for cryptography (RSA).
+This is a PowerShell module for cryptography (RSA).
+
+# Installation
+Module is available on [Powershell Gallery][gallery]
+
+### Install
+```powershell
+PS> Install-Module -Name Crypto.AES
+```
+
+### Import
+```powershell
+PS> Import-Module Crypto.AES
+```
+
+[gallery]: https://www.powershellgallery.com/packages/Crypto.AES