feat: Define node types and create React Flow node components

[lornakelly]

Description

Create react flow node types and the node components associated with them (Custom nodes) for the 12 task types defined in the Serverless Workflow specification.

Motivation

Before React Flow nodes can be built from the workflow model, the task types need to be defined so the model and translation to React Flow have something meaningful to map to.

Proposed Implementation

• Create a directory named "nodes" under "react-flow" to host node custom components specifics.
• The custom node components shall temporarily display task type and label.
• Update the hardcoded diagram to showcase all 12 supported node types.

Definition of Done

• Implementation: Fully implemented according to the Serverless Workflow spec.
• Unit Tests: Comprehensive unit tests are included and passing.
• Integration Tests: Verified within the monorepo and target environments (Web/VS Code).
• Documentation: Updated README.md, ADRs, or official docs.
• Performance: No significant regression in editor responsiveness.
• Accessibility: UI changes comply with accessibility standards.