[Peek] Opening a file via the CLI errors if the path is relative

### Microsoft PowerToys version

0.100.2

### Installation method

Dev build in Visual Studio

### Area(s) with issue?

Peek

### Steps to reproduce

1. Open PowerShell.
2. Navigate to the folder containing the image you want to open.
3. Enter:

```pwsh
\PowerToys.Peek.UI.exe testfile.jpg
```

### ✔️ Expected Behavior

The media is shown.

### ❌ Actual Behavior

An error is shown:

### Upload Bug Report ZIP-file

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### Additional Information

_No response_

### Other Software

_No response_