Update to support node server SDK 7.0 and greater. (#14)

Author: kinyoklion

package.json

@@ -22,7 +22,7 @@
     "jest": "^27.0.4",
     "jest-junit": "^12.2.0",
     "launchdarkly-js-test-helpers": "^1.2.1",
-    "launchdarkly-node-server-sdk": "^6.0.0",
+    "launchdarkly-node-server-sdk": "^7.0.0",
     "prettier": "^2.3.1",
     "typescript": "^4.3.2"
   },
@@ -40,7 +40,7 @@
     "node-cache": "4.2.0"
   },
   "peerDependencies": {
-    "launchdarkly-node-server-sdk": "^6.0.0"
+    "launchdarkly-node-server-sdk": "^6.0.0 || ^7.0.0"
   },
   "engines": {
     "node": ">= 12.0"