Added config for next app router

[jdjfisher]

Next.js sites built with the App Router no longer support a static export via the next export command.

Instead output: 'export' should be added to the configuration to export the static assets to ./out while building with next build.

This configation option should only throw a warning for sites built with Pages Router in older versions of Next.js so it should be safe to introduce in to existing builds.

- error "next export" does not work with App Router. Please use "output: export" in next.config.js https://nextjs.org/docs/advanced-features/static-html-export

[zvailanu98]

• name: Setup .NET Core SDK
  uses: actions/setup-dotnet@v3.2.0
  with:

  Optional SDK version(s) to use. If not provided, will install global.json version when available. Examples: 2.2.104, 3.1, 3.1.x, 3.x, 6.0.2xx

  dotnet-version: # optional

  Optional quality of the build. The possible values are: daily, signed, validated, preview, ga.

  dotnet-quality: # optional

  Optional global.json location, if your global.json isn't located in the root of the repo.

  global-json-file: # optional

  Optional package source for which to set up authentication. Will consult any existing NuGet.config in the root of the repo and provide a temporary NuGet.config using the NUGET_AUTH_TOKEN environment variable as a ClearTextPassword

  source-url: # optional

  Optional OWNER for using packages from GitHub Package Registry organizations/users other than the current repository's owner. Only used if a GPR URL is also provided in source-url

  owner: # optional

  Optional NuGet.config location, if your NuGet.config isn't located in the root of the repo.

  config-file: # optional

  Optional input to enable caching of the NuGet global-packages folder

  cache: # optional

  Used to specify the path to a dependency file: packages.lock.json. Supports wildcards or a list of file names for caching multiple dependencies.

  cache-dependency-path: # optional