Preview %startuml/%enduml block within Markdown does not work in Mac OS

[scmdavid]

Hi,

Mac OS: 12.4
VSCode:1.68.1
PlantUML Extension: v2.17.3

When PlantUML block was embedded in a Markdown file (.md), the graph could not be zoomed. One way to workaround is to move the cursor within a PlantUML block and press ALT + D (Option + D in Mac); it triggers the PlantUML preview, which can be zoomed. However, it only worked in Windows, not MacOS; it did not start a preview.

An example (an .md file),

# Test

## Graph #1

```plantuml
@startuml
a->b
@enduml
```

## Graph #2

```plantuml
@startuml
a->c
@enduml
```

When moving the cursor in the a->b line and pressing ALT + D, PlantUML will render the image of that block in Windows but did not work in Mac OS