docs: align regexp/extended-length-path with namespace conventions

- Added missing `@example` block to `lib/main.js` JSDoc (present in
  26/27 siblings, 96%), adapted from the README usage examples.

https://claude.ai/code/session_0151TCuqxNJXJZfy4XEWqKhM

Author: claude

lib/node_modules/@stdlib/regexp/extended-length-path/lib/main.js

@@ -24,6 +24,14 @@
 * Returns a regular expression that matches an extended-length path.
 *
 * @returns {RegExp} regular expression
+*
+* @example
+* var RE_EXTENDED_LENGTH_PATH = reExtendedLengthPath();
+* var bool = RE_EXTENDED_LENGTH_PATH.test( '\\\\?\\C:\\foo\\bar' );
+* // returns true
+*
+* bool = RE_EXTENDED_LENGTH_PATH.test( 'C:\\foo\\bar' );
+* // returns false
 */
 function reExtendedLengthPath() {
 	return /^\\\\\?\\.+/;