[Docs]: Add documentation and launch instructions for chart_lab world and dispatch_zone task #372

Documentation Issue / Feature Request

Description

PR #350 recently introduced the chart_lab demonstration world and the dispatch_zone CLI task script for the GoToZone capability.

However, neither the main rmf_demos/README.md nor rmf_demos_tasks/README.md have been updated with documentation or example commands for these new additions:

1. README.md does not list the chart_lab world under the "Worlds" section (missing instructions to run ros2 launch rmf_demos_gz chart_lab.launch.xml and ros2 launch rmf_demos chart_lab.launch.xml).
2. rmf_demos_tasks/README.md does not document the new dispatch_zone CLI tool, its arguments (e.g. --zone, -pt, -F, -R), or example usage commands.

Proposed Solution

• Add a new section for ### Chart Lab World in README.md explaining the scenario and how to launch it.
• Add documentation and usage examples for dispatch_zone under the "Flexible Tasks" section in rmf_demos_tasks/README.md.

I would be happy to submit a PR to document these additions!