docs: add docs for Camunda integration

[daveomri]

Summary

• Add comprehensive documentation for the Apify Camunda Connector, covering outbound operations (Run Actor, Run Task, Scrape single URL, Get dataset items, Get key-value store record) and all four inbound connector types (Start Event, Message Start Event, Intermediate Catch Event, Boundary Event)
• Include step-by-step tutorial, Deploy vs Play mode guide, usage patterns, reference tables, and troubleshooting
• Add 19 screenshots for Camunda Modeler and Operate UI walkthrough