Add reason to Cancel Workflow confirmation modal

[laurakwhit]

[HOLD] Waiting on support for reason in cancel event attributes

Description & motivation 💭

Adds a reason input to the cancel confirmation modal when canceling a workflow.

Screenshots (if applicable) 📸

Before	After

Design Considerations 🎨

Testing 🧪

How was this tested 👻

• [ ] Manual testing
• [ ] E2E tests added
• [ ] Unit tests added

Steps for others to test: 🚶🏽‍♂️🚶🏽‍♀️

Checklists

Draft Checklist

Merge Checklist

Issue(s) closed

Docs

Any docs updates needed?