Update README.md (#82)

README.md

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-    EU Digital Green Certificates Issuance Web Frontend
+    EU Digital COVID Certificate Issuance Web Frontend
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@@ -19,7 +19,7 @@
 
 ## About
 
-This repository contains the source code of the Digital Green Certificates Issuance Web Frontend.
+This repository contains the source code of the EU Digital COVID Certificate Issuance Web Frontend.
 
 The issuer application frontend provides a user interface that is used by the issuer to enter the necessary data for DGC issuance.