feat: custom lint rule, fixed readme

.markdownlint-rules/one-sentence-per-line.mjs

@@ -0,0 +1,48 @@
+// @ts-check
+
+/**
+ * @typedef {object} ErrorInfo
+ * @property {number} lineNumber
+ * @property {string} [context]
+ * @property {string} [detail]
+ * @property {[number, number]} [range]
+ */
+
+/**
+ * @typedef {object} Params
+ * @property {string[]} lines
+ */
+
+/** @typedef {(error: ErrorInfo) => void} OnError */
+
+/**
+ * @typedef {object} Rule
+ * @property {string[]} names
+ * @property {string} description
+ * @property {string[]} tags
+ * @property {(params: Params, onError: OnError) => void} function
+ */
+
+/** @type {Rule} */
+export default {
+  names: ["one-sentence-per-line"],
+  description: "Each sentence must be on its own line",
+  tags: ["sentences"],
+  function: function (params, onError) {
+    let inFence = false;
+    params.lines.forEach((line, index) => {
+      if (/^```/.test(line)) {
+        inFence = !inFence;
+        return;
+      }
+      if (inFence) return;
+      // Skip headings, blank lines, HTML, table rows
+      if (/^(#|\s*[|<]|>|\s*$)/.test(line)) return;
+      // Strip list marker before checking
+      const text = line.replace(/^\s*(?:[-*+]|\d+\.)\s+/, "");
+      if (/[.!?]\s+[A-Z]/.test(text)) {
+        onError({ lineNumber: index + 1, context: text.trim() });
+      }
+    });
+  },
+};