Add npm keywords

Author: ehmicky

package.json

@@ -12,7 +12,28 @@
     "test": "gulp test"
   },
   "description": "JSON serialization should never fail",
-  "keywords": [],
+  "keywords": [
+    "bigint",
+    "circular",
+    "cycle",
+    "enumerable",
+    "exception-handling",
+    "exceptions",
+    "getters",
+    "javascript",
+    "json",
+    "library",
+    "nodejs",
+    "parsing",
+    "serialization",
+    "symbols",
+    "tojson",
+    "types",
+    "typescript",
+    "valid",
+    "validate",
+    "validation"
+  ],
   "license": "Apache-2.0",
   "homepage": "https://www.github.com/ehmicky/safe-json-value",
   "repository": "ehmicky/safe-json-value",