fix: Add DD to alias_key.json

Author: corneliusroemer

pango_designation/alias_key.json

@@ -88,6 +88,7 @@
     "DA": "B.1.1.529.5.2.38",
     "DB": "B.1.1.529.5.2.25",
     "DC": "B.1.1.529.4.6.5",
+    "DD": "B.1.1.529.2.3.21",
     "XA": ["B.1.1.7","B.1.177"],
     "XB": ["B.1.634","B.1.631"],
     "XC": ["AY.29","B.1.1.7"],