Refactor code-style

*   Add more docs to JSDoc

lib/index.js

@@ -4,6 +4,9 @@ import {start as startRe, cont as contRe} from './regex.js'
  * Checks if the given character code can start an identifier.
  *
  * @param {number} code
+ *   Character code to check.
+ * @returns {boolean}
+ *   Whether `code` can start an identifier.
  */
 // To do: support astrals.
 export function start(code) {
@@ -14,6 +17,9 @@ export function start(code) {
  * Checks if the given character code can continue an identifier.
  *
  * @param {number} code
+ *   Character code to check.
+ * @returns {boolean}
+ *   Whether `code` can continue an identifier.
  */
 // To do: support astrals.
 export function cont(code) {
@@ -25,6 +31,9 @@ export function cont(code) {
  * Checks if the given string is a valid identifier name.
  *
  * @param {string} name
+ *   Identifier to check.
+ * @returns {boolean}
+ *   Whether `name` can be an identifier.
  */
 export function name(name) {
   let index = -1