Docs: Improve click tracking example

A few things that improve this example IMO - remove `isPjax` reference which [looks like](https://www.google.com/search?q=isPjax) something from laravel(?) and is [not part of the codebase](https://github.com/search?q=repo%3Ananostores%2Frouter%20isPjax&type=code) - add `preventDefault` which is needed here IMO - use `openPage` which is a nice helper to use here IMO - suggest preserving the page search params with `params`