Allow wsconfig.json to define overrides for Debug/Release configurations

[Jand42]

To allow changing the bundling behavior for Release/Debug builds, we can extend wsconfig.json with relevant sections. For instance, the following sets up "prebundling" in release mode:

For example:

{
  "$schema": "https://websharper.com/wsconfig.schema.json",
  "project": "web",
  "outputDir": "wwwroot",
  "release": {
    "outputDir": "build",
    "preBundle": true
  }
}