Prompt user to install Blazor WASM companion extension if needed

[captainsafia]

Detects if the companion extension is installed if the user is editing a Blazor WASM project and prompts them to install it if not.

The companion extension is a new requirement for debugging Blazor WASM on VS Code to allow for:

• support for remote debugging
• faster launching for debugging sessions
• ability to debug on apps with windows auth configured

[JoeRobich]

LGTM. If this were a behavior you would like the vendors to test as part of release validation, then you could add a section to the test-plan.

[NTaylorMullen]

What's the debug experience if the user doesn't have the companion installed?

[captainsafia]

If this were a behavior you would like the vendors to test as part of release validation, then you could add a section to the test-plan.

Updated the test plan.

What's the debug experience if the user doesn't have the companion installed?

The user will be able to run the the app and open it in a standard browser but the debugging browser will not launch.