(build) Update appveyor build script

We still want things to build on AppVeyor, so going to borrow the
configuration that is currently in place for Cake.Issues.Recipe, and
hopefully the failing build on AppVeyor for start working.

.appveyor.yml

@@ -1,4 +1,18 @@
-image: Visual Studio 2019
+image: Visual Studio 2022
+
+#---------------------------------#
+#  Install .NET                   #
+#---------------------------------#
+install:
+  - ps: $env:DOTNET_INSTALL_DIR = "$pwd\.dotnetsdk"
+  - ps: mkdir $env:DOTNET_INSTALL_DIR -Force | Out-Null
+  - ps: Invoke-WebRequest -Uri "https://dotnet.microsoft.com/download/dotnet/scripts/v1/dotnet-install.ps1" -OutFile "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1"
+  - ps: '& "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1" -Version 5.0.408 -InstallDir $env:DOTNET_INSTALL_DIR'
+  - ps: '& "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1" -Version 6.0.421 -InstallDir $env:DOTNET_INSTALL_DIR'
+  - ps: '& "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1" -Version 7.0.408 -InstallDir $env:DOTNET_INSTALL_DIR'
+  - ps: '& "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1" -Version 8.0.204 -InstallDir $env:DOTNET_INSTALL_DIR'
+  - ps: $env:Path = "$env:DOTNET_INSTALL_DIR;$env:Path"
+  - ps: dotnet --info
 
 #---------------------------------#
 #  Build Script                   #