Evaluate DSPF Designer for the IBM i Development Pack

## Context

The pack currently includes:

`HalcyonTechLtd.vscode-displayfile`

The repository for this extension indicates that the old renderer is deprecated and that development has moved toward a new DDS renderer/editor:

https://github.com/codefori/vscode-ibmi-renderer

## Proposal

I would like to propose evaluating DSPF Designer for inclusion in the IBM i Development Pack.

Marketplace:
https://marketplace.visualstudio.com/items?itemName=Balrocj.dspf-designer

Repository:
https://github.com/Balrocj/dspf-designer

DSPF Designer is an open-source visual editor for IBM i DDS display files. The project has recently reached version 2.8.0 and is now considered stable for general use.

It currently provides:

* Drag-and-drop screen design
* DDS generation
* Field properties and indicators
* Multiple display sizes
* Live preview
* Direct source editing
* Save support for existing DSPF files

Given that the renderer currently included in the pack is deprecated, I thought DSPF Designer might be useful to consider as an additional tool for developers working with DSPF files.

## Possible approach

DSPF Designer could initially be added alongside the existing renderer, allowing users to use the renderer for its existing capabilities while also having access to visual DSPF editing.

If the maintainers think it would be a good fit for the pack, I would be happy to provide a pull request.

No project file or test is named. Start by reviewing the DSPF Designer marketplace and repository links, then inspect how the IBM i Development Pack currently includes the deprecated renderer. Done means the maintainers decide whether DSPF Designer fits and, if accepted, define the inclusion change and its validation.

Written by the indexing model from the issue text.