desire to have a way to list relevant (changed) features

idk if this is the right spot to bring this up but hey 🤷‍♀️

I've recently found immense usefulness in being able to list which features changed and default to all of them if the changes cant be determined https://github.com/devcontainers-community/list-features (no its not very polished yet)

i notice that there seems to be an attempt to do this in the feature-starter repo:

```yml
strategy:
matrix:
features: # 👈
- color
- hello
baseImage:
- debian:latest
- ubuntu:latest
- mcr.microsoft.com/devcontainers/base:ubuntu
```

I think it's very nice to be able to do this instead:

```yml
list-features:
outputs:
relevant-features: ${{ steps.list-features.outputs.relevant-features }}
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v3
with:
fetch-depth: 0
- id: list-features
uses: devcontainers-community/list-features@v2

strategy:
fail-fast: false
matrix:
include: ${{ fromJSON(needs.list-features.outputs.relevant-features) }}

# then do this
${{ matrix.id }} ${{ matrix.documentationURL }}
```
or this if you prefer to matrix your image too (disclaimer haven't tested this flow yet)
```yml
strategy:
fail-fast: false
matrix:
feature: ${{ fromJSON(needs.list-features.outputs.relevant-features) }}
image:
- debian:latest
- ubuntu:latest
- mcr.microsoft.com/devcontainers/base:ubuntu

# then do this
${{ matrix.feature.id }} ${{ matrix.image }} ${{ matrix.feature.documentationURL }}
```

used in a repo like this
https://github.com/devcontainers-community/npm-features/blob/main/.github/workflows/test-features.yml

demo of it in action
https://github.com/devcontainers-community/npm-features
ex: 

id to see this thing into the official @devcontainers feaeture-starter or organization if that's possible. idk if this is completely breaking some kind of unspoken project ettiqute; i just want this thing to be "official" since it seems so cool.