add npm keywords

package.json

@@ -51,5 +51,12 @@
     "ts-node": "~7.0.0",
     "tslint": "~6.1.0",
     "typescript": "~3.9.7"
-  }
-}
+  },
+  "keywords": [
+    "typescript",
+    "html",
+    "json",
+    "xml",
+    "json-to-html"
+  ]
+}
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