Image content not visible on Dark Theme

### Type of issue

Other (describe below)

### Description

[Enter feedback here]
When viewing this page in the Dark Theme, the black parts of the image (arrows and text) are not visible.
The image needs a background so that it can be viewed in all themes.

### Page URL

https://learn.microsoft.com/en-us/dotnet/csharp/roslyn-sdk/work-with-workspace?source=docs

### Content source URL

https://github.com/dotnet/docs/blob/main/docs/csharp/roslyn-sdk/work-with-workspace.md

### Document Version Independent Id

cf27be4d-743f-65b6-be69-3e78e7da9908

### Article author

@BillWagner

### Metadata

* ID: 77f42c43-e155-720a-2bb5-f92584205486
* Product: **dotnet-csharp**
* Technology: **csharp-roslyn**