Add D language version

d/dub.json

@@ -0,0 +1,16 @@
+{
+    "name": "GildedRose",
+    "configurations": [
+        {
+            "name": "GuildedRose",
+            "targetType": "executable",
+            "mainSourceFile": "src/GildedRoseTextTests.d"
+        },
+        {
+            "name": "unittest",
+            "targetType": "executable",
+            "sourcePaths": ["test"],
+            "mainSourceFile": "test/GildedRoseUnitTests.d"
+        }
+    ]
+}