[build] tweak mlc config path

.github/mlc_config.json

@@ -0,0 +1,10 @@
+{
+    "ignorePatterns": [
+        {
+            "pattern": "^/assets"
+        },
+        {
+            "pattern": "^https://archive.org"
+        }
+    ]
+}

.github/workflows/check-md-links.yml

@@ -9,4 +9,4 @@ jobs:
       - uses: actions/checkout@master
       - uses: gaurav-nelson/github-action-markdown-link-check@v1
         with:
-          config-file: 'mlc_config.json'
+          config-file: '.github/mlc_config.json'