chore: Add Markdownlint (#2354)

1. Add Markdownlint checking for Markdown files
2. Add .markdownlint.json to disable all non-passing rules to start
3. Add markdownlint run to the test:lint target

Author: nschonni

.markdownlint.json

@@ -0,0 +1,36 @@
+{
+  "default": true,
+  "MD001": false,
+  "MD004": false,
+  "MD005": false,
+  "MD006": false,
+  "MD007": false,
+  "MD009": false,
+  "MD010": false,
+  "MD012": false,
+  "MD013": false,
+  "MD014": false,
+  "MD018": false,
+  "MD019": false,
+  "MD022": false,
+  "MD024": false,
+  "MD025": false,
+  "MD026": false,
+  "MD027": false,
+  "MD028": false,
+  "MD029": false,
+  "MD030": false,
+  "MD031": false,
+  "MD032": false,
+  "MD033": false,
+  "MD034": false,
+  "MD035": false,
+  "MD036": false,
+  "MD038": false,
+  "MD039": false,
+  "MD040": false,
+  "MD041": false,
+  "MD042": false,
+  "MD046": false,
+  "MD047": false
+}

package-lock.json

@@ -14,7 +14,7 @@
     "load-schedule": "curl -sS https://raw.githubusercontent.com/nodejs/Release/master/schedule.json -o source/schedule.json",
     "start": "npm run serve",
     "test": "npm run test:lint && npm run test:unit && npm run test:smoke",
-    "test:lint": "standard --fix && htmllint **/*.hbs && stylint layouts/css",
+    "test:lint": "standard --fix && htmllint **/*.hbs && stylint layouts/css && markdownlint \"**/*.md\" -i \"node_modules/\"",
     "test:unit": "tape tests/**/*.test.js | faucet",
     "test:smoke": "tape tests/*.smoketest.js | faucet"
   },
@@ -64,6 +64,7 @@
   "devDependencies": {
     "faucet": "^0.0.1",
     "htmllint-cli": "^0.0.6",
+    "markdownlint-cli": "^0.17.0",
     "nock": "^10.0.6",
     "pre-commit": "^1.2.2",
     "proxyquire": "^2.0.1",