Update required Node.js version to 10 (8 is no longer supported).

DavidAnson · DavidAnson · commit a1713b787508 · 2020-02-08T11:09:39.000-08:00
diff --git a/package.json b/package.json
@@ -7,7 +7,7 @@
     "markdownlint": "markdownlint.js"
   },
   "engines": {
-    "node": ">=8"
+    "node": ">=10"
   },
   "scripts": {
     "invalid": "node ./markdownlint.js --config test/test-config.json -- test/incorrect.md",
