feat(examples/container): move to examples, convert to TS, render collapse button via highlighter

[zbynekstara]

Description

Converts joint/demo/container into TS and moves to examples/container.

Renders containers' collapse/expand buttons with a highlighter, instead of hard-coding them in their markup.

Motivation and Context

Using highlighters for this purpose is a better practice, since they can be mixed-and-matched with any shape.

[Copilot]

Pull Request Overview

This PR implements improvements to container components by rendering collapse/expand buttons via a custom highlighter instead of embedding them directly in the markup. Key changes include refactoring container shape definitions, updating the toggle behavior and event handling in the diagram, and adding custom CSS for improved visual consistency.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/joint-core/demo/container/src/joint.shapes.container.js	Refactored container shapes definitions, updated constants, and modified the toggle method to delegate collapse/expand rendering.
packages/joint-core/demo/container/src/index.js	Introduced a cellNamespace, implemented an ExpandButtonHighlighter to handle button rendering, and revised event handlers for container size updates.
packages/joint-core/demo/container/css/container.css	Added CSS styles for the paper border and margin adjustments.

Comments suppressed due to low confidence (1)

packages/joint-core/demo/container/src/joint.shapes.container.js:139

• The toggle method no longer updates the button icon attribute, so please ensure that the highlighter component reliably updates the collapse/expand icon to avoid any visual inconsistencies.

this.set('collapsed', typeof shouldCollapse === 'boolean' ? shouldCollapse : !this.get('collapsed'));

[Copilot]

Pull Request Overview

This PR migrates the JointJS container demo from the legacy JavaScript implementation in packages/joint-core to a new TypeScript-based demo in the examples folder while updating the collapse/expand button rendering to use a highlighter.

• Moved container demo code from packages/joint-core to examples/container
• Converted code to TypeScript and updated the webpack configuration
• Introduced a highlighter-based rendering for container collapse/expand buttons

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/joint-core/demo/container/*	Removed legacy JS implementation
examples/container/webpack.config.js	Added webpack configuration for TS builds
examples/container/tsconfig.json	Added TS configuration
examples/container/src/shapes.ts	New TS definitions for Container, Child, and Link
examples/container/src/index.ts	Updated TS entry point with highlighter logic and interactive tools
examples/container/package.json	Package configuration for the new demo
examples/container/index.html & index.css	HTML and CSS updates to support the new build output
examples/container/README.md & .gitignore	Updated documentation and ignore rules for the new demo