How to use docker buildx ls command to list builder instances

# Introduction

In this lab, you will learn how to use the `docker buildx ls` command to list builder instances and their associated nodes. You will explore the basic usage of the command to view available build environments and their configurations.

Furthermore, you will discover how to format the output of `docker buildx ls` using Go templates to customize the displayed information. This includes formatting the output to show specific fields and to visualize the relationships between builder instances and their nodes.