prepare 2.20.0 release (#43)

Author: LaunchDarklyCI

package-lock.json

@@ -56,7 +56,7 @@
     "typescript": "~3.8.3"
   },
   "dependencies": {
-    "launchdarkly-js-client-sdk": "2.17.6",
+    "launchdarkly-js-client-sdk": "2.18.0",
     "lodash.camelcase": "^4.3.0",
     "uuid": "^3.3.2"
   },