Add SBOM extraction instructions

Author: thomasleplus

README.md

@@ -7,3 +7,22 @@ Docker image to run the AWS CLI and related tools.
 [![Docker Stars](https://img.shields.io/docker/stars/leplusorg/aws-cli)](https://hub.docker.com/r/leplusorg/aws-cli)
 [![Docker Pulls](https://img.shields.io/docker/pulls/leplusorg/aws-cli)](https://hub.docker.com/r/leplusorg/aws-cli)
 [![Docker Version](https://img.shields.io/docker/v/leplusorg/aws-cli?sort=semver)](https://hub.docker.com/r/leplusorg/aws-cli)
+
+## Usage
+
+To run the AWS CLI using this image:
+
+```bash
+docker run --rm -i leplusorg/aws-cli aws --version
+```
+
+## Software Bill of Materials (SBOM)
+
+To get the SBOM for the latest image (in SPDX JSON format), use the
+following command:
+
+```bash
+docker buildx imagetools inspect leplusorg/aws-cli --format '{{ json (index .SBOM "linux/amd64").SPDX }}'
+```
+
+Replace `linux/amd64` by the desired platform (`linux/amd64`, `linux/arm64` etc.).