The `runner.environment` context is shown as invalid in this extension.

**Describe the bug**
When we use the `runner.environment` context listed in [official document](https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/accessing-contextual-information-about-workflow-runs#runner-context), this extension reports "Context access might be invalid".

**To Reproduce**
Steps to reproduce the behavior:
1. With this workflow '...'

```yaml
steps:
- if: ${{ runner.environment == 'github-hosted' }}
run: echo "This is a ${{ runner.environment }} runner"
```

2. Do this '...'

Open the "Problems" Panel.

3. See error\

```plain
Context access might be invalid: environment
```

**Expected behavior**
The `runner.environment` context listed in [official document](https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/accessing-contextual-information-about-workflow-runs#runner-context) can be recognized well by this extension.

**Screenshots**

**Extension Version**
`v0.27.0`

**Additional context**
Add any other context about the problem here.

まず、提供された workflow スニペットを拡張機能で再現し、Problems-panel の警告を生成するコンテキスト検証パスを調査します。runner.environment がリンク先の GitHub Actions の runner コンテキストに関するドキュメントに従って認識され、この式に対する警告が表示されなくなれば、作業は完了です。

索引モデルが issue の本文から書いたものです。