Markdown lint ignore github docs

See #701

Author: rajsite

.linkcheck.json

@@ -0,0 +1,7 @@
+{
+    "ignorePatterns": [
+        {
+            "pattern": "https://help.github.com/*"
+        }
+    ]
+}

package.json

@@ -39,7 +39,7 @@
     "test-asmjs": "karma start karma.asmjs.conf.js --browsers ChromeHeadlessNoSandbox,FirefoxHeadless",
     "lint": "eslint .",
     "lint-markdown": "npm run lint-markdown-style && npm run lint-markdown-links",
-    "lint-markdown-links": "glob-exec --foreach \"{./*.md,./docs/*.md}\" -- \"npm run markdown-link-check -- {{file}}\"",
+    "lint-markdown-links": "glob-exec --foreach \"{./*.md,./docs/*.md}\" -- \"npm run markdown-link-check -- -c .linkcheck.json {{file}}\"",
     "markdown-link-check": "markdown-link-check",
     "lint-markdown-style": "markdownlint {./*.md,./docs/*.md}",
     "prehttpbin": "python -V && pip -V && virtualenv --version && tox --version",