Discussion + Feature: LTS vs Experimental DFDL language extensions

# Discussion + Feature: LTS vs Experimental DFDL language extensions

## Problem Description

See https://lists.apache.org/thread/39mnq6cg1x12dpkk0tv8ggbcydbl9lqt for context. DFDL language extensions have been added per the conversations. (see https://github.com/apache/daffodil-site/commit/17f2e9c58ab3fb775a9adb8c8252309147ba4c8e)

```
The LTS implications would include having real documentation of the features (which I am working on) on the daffodil-site, whereas the experimental would be documented with Wiki pages only. Also the LTS features really could/should eventually have support from the VSCode extension for Daffodil as if they were officially part of DFDL. They are mostly very easy to support. Only dfdlx:layer is hard - and that one is quite a challenge for a visual GUI tool.
```

## Proposed Solution

Consult with Mike Beckerlie on usage and information about the extension's attributes/elements.

Go forward from there.

## User Stories (Optional but Recommended)

TBD

## Acceptance Criteria

TBD

## Impact and Benefits

Keeps the extension's functionalities in-line with additions to DFDL

## Open Questions / Discussion Points (Optional)

How do we approach resolving this ticket in terms of breaking it down? It should be noted too that this ticket will be related to #1514.

Begin with the linked mailing-list discussion, the daffodil-site commit, and related issue #1514 to understand the proposed language extensions. Consult Mike Beckerlie about the attributes and elements, then define a concrete breakdown separating LTS and experimental work. Done should include agreed scope and acceptance criteria rather than TBD discussion points.

Written by the indexing model from the issue text.