docs : add WeTransfer to 'Who uses Amundsen?' (#705)

* docs : add WeTransfer to 'Who uses Amundsen?'
Signed-off-by: higee <gshock94@gmail.com>

* docs : sort 'Who uses Amundsen?' alphabetically
Signed-off-by: higee <gshock94@gmail.com>

README.md

@@ -214,6 +214,7 @@ Currently **officially** using Amundsen:
 1. [PUBG](https://careers.pubg.com/)
 1. [Remitly](https://www.remitly.com/)
 1. [Square](https://squareup.com/us/en)
+1. [WeTransfer](https://wetransfer.com)
 1. [Workday](https://www.workday.com/en-us/homepage.html)
 
 # License