Add first business article and article layout

node_modules/mdast-util-to-markdown/lib/util/check-rule.js

@@ -0,0 +1,21 @@
+/**
+ * @import {Options, State} from 'mdast-util-to-markdown'
+ */
+
+/**
+ * @param {State} state
+ * @returns {Exclude<Options['rule'], null | undefined>}
+ */
+export function checkRule(state) {
+  const marker = state.options.rule || '*'
+
+  if (marker !== '*' && marker !== '-' && marker !== '_') {
+    throw new Error(
+      'Cannot serialize rules with `' +
+        marker +
+        '` for `options.rule`, expected `*`, `-`, or `_`'
+    )
+  }
+
+  return marker
+}