Improve VS Code instructions in tutorials

1. The docs recommend pressing Ctrl+F5 to generate launch.json/tasks.json, there is a better way –
a. The C# extension ideally will prompt you with “Required assets to build and debug are missing…”. If so, just click “Yes”.
-or-
b. Sometimes the C# extension will fail to put up that prompt. You can force it using “.NET: Generate Assets for Build and Debug” from the VS Code command well:

2. Modify `serverReadyAction` in launch.json to point at the swagger endpoint in Web API tutorials. Add uriFormat:
```
"serverReadyAction": {
"action": "openExternally",
"pattern": "\\bNow listening on:\\s+(https?://\\S+)",
"uriFormat": "%s/swagger"
},
```

4. F5/Ctrl-F5 will default to launching a browser, so no need to do that