Blazor Debugging in VS Browser KeepAlive

This issue is broken off into two parts:

1. [aspnetcore-browser-refresh.js:55 Unknown payload: { "type" : "Ping" }](https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1600112)
- We're currently failing to handle the `Ping` message [here](https://github.com/dotnet/sdk/blob/a95405c8c0c21481323322eb9c9e74ded6e98b63/src/BuiltInTools/BrowserRefresh/WebSocketScriptInjection.js#L44-L56)
- We need to handle this message somehow. We can do a simple no-op, however this may be a good opportunity to tackle #2
2. [Running a Blazor web app doesn't always launch the browser](https://dev.azure.com/devdiv/DevDiv/_workitems/edit/1613517)
- https://dev.azure.com/devdiv/DevDiv/_workitems/edit/1613517#3285696
- Essentially making a keepalive mechanism for the browser while debugging.