Refactor code-style

*   Add more docs to JSDoc
*   Add support for `null` in input of API types

Author: wooorm

lib/index.js

@@ -1,22 +1,24 @@
 /**
  * @typedef PointLike
- * @property {number} [line]
- * @property {number} [column]
- * @property {number} [offset]
+ * @property {number | null | undefined} [line]
+ * @property {number | null | undefined} [column]
+ * @property {number | null | undefined} [offset]
  *
  * @typedef PositionLike
- * @property {PointLike} [start]
- * @property {PointLike} [end]
+ * @property {PointLike | null | undefined} [start]
+ * @property {PointLike | null | undefined} [end]
  *
  * @typedef NodeLike
- * @property {PositionLike} [position]
+ * @property {PositionLike | null | undefined} [position]
  */
 
 /**
- * Check if `node` is *generated*.
+ * Check if `node` is generated.
  *
- * @param {NodeLike} [node]
+ * @param {NodeLike | null | undefined} [node]
+ *   Node to check.
  * @returns {boolean}
+ *   Whether `node` is generated (does not have positional info).
  */
 export function generated(node) {
   return (