refactor sources data structure

identify the data source

data/sources.json

@@ -1,3 +1,12 @@
 {
-    "Training_Essay_Data.csv": "sunilthite/llm-detect-ai-generated-text-dataset/versions/1"
+    "LDAG": {
+        "source": "kaggle",
+        "filename": "Training_Essay_Data.csv",
+        "identifier": "sunilthite/llm-detect-ai-generated-text-dataset/versions/1"
+    },
+    "HLTC": {
+        "source": "kaggle",
+        "filename": "data.csv",
+        "identifier": "starblasters8/human-vs-llm-text-corpus/versions/2"
+    }
 }