Update minimum Node version to 10

Node 8 has reached end-of-life.

Author: wimpyprogrammer

package.json

@@ -22,7 +22,7 @@
     "*.scss"
   ],
   "engines": {
-    "node": ">=8"
+    "node": ">=10"
   },
   "scripts": {
     "build": "npm run clean && babel src -d lib --extensions '.js,.ts' --ignore '**/*.spec.js','**/*.spec.ts' && npm run build-types",