Add clearer instructions to experimental content intellisense setup

[JusticeMatthew]

📚 Subject area/topic

content layer

📋 Suggested page

https://docs.astro.build/en/reference/configuration-reference/#experimentalcontentintellisense

📋 General description or bullet points (if proposing new content)

Provide clearer instructions for accessing and enabling the setting in VS Code

🖥️ Reproduction of code samples in StackBlitz

No response