[Shell Panel] add open/close animation

[fdeters]

Check existing issues

• [X] I have checked for existing issues to avoid duplicates

Description

I'd like to be able to configure the calcite-shell-panel component to transition its width on collapse/expand. I could see it being a property like animate-collapse, or potentially configured through CSS variables.

This is most relevant when the shell panel is being used in docked mode next to a large map in the central calcite-shell content area. Opening and closing the shell panel has a somewhat jarring effect.

Acceptance Criteria

• calcite-shell-panel can transition its width on expand/collapse for a smooth open/close effect.
• user can opt in or out of the transition

Relevant Info

No response

Which Component

Shell Panel

Example Use Case

No response

Priority impact

p4 - not time sensitive

Calcite package

• [X] @esri/calcite-components
• [ ] @esri/calcite-components-react
• [ ] @esri/calcite-design-tokens
• [ ] @esri/eslint-plugin-calcite-components

Esri team

N/A