Add Extensions Bundle page to Grafana docs

[heitortsergent]

We have a page in the k6.io/docs that lets users select the extensions they want and build a CLI command to generate the k6 binary they need: https://k6.io/docs/extensions/get-started/bundle/

It would be great if we could have that same functionality in grafana.com/docs/k6 as well.

[heitortsergent]

@immavalls we can use this issue to track this work. :)