Address new TypeScript warnings in core files, improve type definitions.

lib/md029.mjs

@@ -31,7 +31,7 @@ export default {
   "tags": [ "ol" ],
   "parser": "micromark",
   "function": function MD029(params, onError) {
-    const style = String(params.config.style || "one_or_ordered");
+    const style = String(params.config.style);
     for (const listOrdered of filterByTypesCached([ "listOrdered" ])) {
       const listItemPrefixes = getDescendantsByType(listOrdered, [ "listItemPrefix" ]);
       let expected = 1;
@@ -48,10 +48,10 @@ export default {
         }
       }
       // Determine effective style
-      let listStyle = style;
-      if (listStyle === "one_or_ordered") {
-        listStyle = incrementing ? "ordered" : "one";
-      } else if (listStyle === "zero") {
+      const listStyle = ((style === "one") || (style === "ordered") || (style === "zero")) ?
+        style :
+        (incrementing ? "ordered" : "one");
+      if (listStyle === "zero") {
         expected = 0;
       } else if (listStyle === "one") {
         expected = 1;