Replace Camunda screenshots with Operaton examples

[sgort]

Issue

With the fork, the documentation still contains Camunda screenshot images. These need to be replaced with Operaton examples.

To Do

• deploy & host Operaton instance specifically for documentation purposes
• work on Reorganize images into a structured hierarchy that mirrors the documentation structure #48 first
• replace Camunda screenshots in documentation

[sgort]

Operaton instance for documentation

The instance is available at https://operaton-doc.open-regels.nl/ with default credentials. Running behind Caddy reverse proxy.

@a-m-zill if you set the applicable DNS A record for IP Address: 20.123.66.147, I'll change the Caddyfile accordingly. I will also make sure this instance always runs the :latest tagged Docker image.