chore(demo): fix RTL column reordering example

[jahanbakhsh18]

Summary

This PR enables and verifies column reordering in the RTL example.

• Use the existing sortablejs-rtl distribution for the RTL example.
• Enable column reordering in the RTL example.
• Add a note indicating that the RTL-compatible SortableJS distribution is required.
• Add Cypress coverage for column reordering in both directions.

Implementation

Since SlickGrid consumes SortableJS as an external dependency and the examples already load SortableJS from CDN, I chose to use the existing sortablejs-rtl distribution for the RTL example instead of introducing a patched SortableJS dependency through pnpm.

This keeps the change isolated to the RTL example while providing working RTL column reordering with Cypress coverage.

[ghiscoding]

seems ok since it's just for demo purposes, thanks