[update] add markdownlint tool and configure

.markdownlint.json

@@ -0,0 +1,6 @@
+{
+  "MD013": false,
+  "MD034": false,
+  "MD033": false,
+  "MD036": false
+}

.vscode/extensions.json

@@ -1,3 +1,8 @@
 {
-  "recommendations": ["streetsidesoftware.code-spell-checker", "huacnlee.autocorrect", "biomejs.biome"]
+  "recommendations": [
+    "streetsidesoftware.code-spell-checker",
+    "huacnlee.autocorrect",
+    "biomejs.biome",
+    "DavidAnson.vscode-markdownlint"
+  ]
 }