added Servercow to supported list

README.md

@@ -341,7 +341,7 @@ You don't have to do anything manually!
 1. Hurricane Electric DNS service (https://dns.he.net)
 1. UnoEuro API (https://www.unoeuro.com/)
 1. INWX (https://www.inwx.de/)
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+1. Servercow (https://servercow.de)
 
 And: