update dependencies and mark sideEffects free

Author: sergio-toro

package-lock.json

@@ -3,6 +3,7 @@
   "version": "5.0.2",
   "description": "Sensor component for React that notifies you when it goes in or out of the window viewport.",
   "main": "dist/visibility-sensor.js",
+  "sideEffects": false,
   "scripts": {
     "clean": "rm -rf dist && mkdir dist",
     "prebuild": "npm run clean",
@@ -21,8 +22,8 @@
   "author": "joshwnj",
   "license": "MIT",
   "peerDependencies": {
-    "react": ">=16.0.0",
-    "react-dom": ">=16.0.0"
+    "react": ">=16.8.0",
+    "react-dom": ">=16.8.0"
   },
   "devDependencies": {
     "babel-core": "^6.26.3",
@@ -39,8 +40,8 @@
     "lint-staged": "^7.3.0",
     "mocha": "^5.2.0",
     "prettier": "1.14.3",
-    "react": "^16.4.2",
-    "react-dom": "^16.4.2",
+    "react": "^16.8.6",
+    "react-dom": "^16.8.6",
     "uglify-js": "^3.4.6",
     "uglifyjs-webpack-plugin": "^2.0.1",
     "webpack": "^4.16.4",