docs: Add badges for quick information
It would useful to quickly get some information regrading the repository especially the CI status. So, I propose to add these badges.
Fixes
</picture>
</h1>
+[![Inspektor Gadget CI](https://github.com/inspektor-gadget/inspektor-gadget/actions/workflows/inspektor-gadget.yml/badge.svg)](https://github.com/inspektor-gadget/inspektor-gadget/actions/workflows/inspektor-gadget.yml)
+[![Go Reference](https://pkg.go.dev/badge/github.com/inspektor-gadget/inspektor-gadget.svg)](https://pkg.go.dev/github.com/inspektor-gadget/inspektor-gadget)
+[![Go Report Card](https://goreportcard.com/badge/github.com/inspektor-gadget/inspektor-gadget)](https://goreportcard.com/report/github.com/inspektor-gadget/inspektor-gadget)
+[![Release](https://img.shields.io/github/v/release/inspektor-gadget/inspektor-gadget)](https://github.com/inspektor-gadget/inspektor-gadget/releases)
+[![Slack](https://img.shields.io/badge/slack-%23inspektor--gadget-brightgreen.svg?logo=slack)](https://kubernetes.slack.com/messages/inspektor-gadget/)
+[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://github.com/inspektor-gadget/inspektor-gadget/blob/main/LICENSE)
+[![License: GPL v2](https://img.shields.io/badge/License-GPL%20v2-blue.svg)](https://github.com/inspektor-gadget/inspektor-gadget/blob/main/LICENSE-bpf.txt)
+
Inspektor Gadget is a collection of tools (or gadgets) to debug and inspect
Kubernetes resources and applications. It manages the packaging, deployment and
execution of [eBPF](https://ebpf.io/) programs in a Kubernetes cluster,
