Additional steps for the cosign contract

For the contract with cosign verified container images, perform the following additional steps:

Log in to your Quay registry by running the following command:
```
docker login quay.io -u <username> -p <password>
```
Pull the container image onto your local machine.
```
docker pull quay.io/prometheus/busybox:latest
```
Tag the container image to your repository in the Quay registry by running the following command:
```
docker tag quay.io/prometheus/busybox:latest quay.io/<username>/busybox:latest
```
Push the container image to your repository in the Quay registry by running the following command:
```
docker push quay.io/<username>/busybox
```

Install the Cosign Package by running the following command:

rpm -ivh --nodeps --force https://github.com/sigstore/cosign/releases/download/v2.4.1/cosign-2.4.1-1.s390x.rpm

Log in to your Quay registry using cosign by running the following command:
```
cosign login quay.io --username='<username>' --password='<password>'
```
Generate a key pair to sign the container image.
```
cosign generate-key-pair
```
This creates cosign.key and cosign.pub.
Sign and verify the container image in the Quay registry with the private key by running the following command:
```
cosign sign --key cosign.key quay.io/<username>/busybox
```
Encode and store the public key you obtained from the earlier step in a variable by running the following command:
```
export cosign_pub_base64=$(cat "cosign.pub" | base64 -w 0)
```
Continue with Step 5 from Creating the workload section of the contract section.