fix: Update minimum node version to 8.9.0 (#989)

Author: LukeHowellDev

package.json

@@ -28,7 +28,7 @@
     "buildifier": "find . -type f \\( -name BUILD -or -name BUILD.bazel \\) ! -path \"*/node_modules/*\" | xargs $(bazel info bazel-bin)/external/com_github_bazelbuild_buildtools/buildifier/*/buildifier"
   },
   "engines": {
-    "node": ">=8.6.0",
+    "node": ">=8.9.0",
     "npm": ">=5.3.0",
     "yarn": ">=1.3.0 <2.0.0"
   },