(doc) Added more information about upgrade

Also, add in another .NET Core version, as Wyam still seems to be
getting hung up, and not actually publishing.

.appveyor.yml

@@ -7,6 +7,7 @@ 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 2.1.818 -InstallDir $env:DOTNET_INSTALL_DIR'
  - ps: '& "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1" -Version 3.1.426 -InstallDir $env:DOTNET_INSTALL_DIR'
  - ps: '& "$($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'

docs/input/docs/upgrading/3.x-to-4.x.md

@@ -8,4 +8,10 @@ Description: Changes and suggestions needed for porting from Cake.Recipe 3.x to
 
 ### Switch to using Cake 2.3.0
 
-Cake.Recipe is now using 2.3.0 of Cake, and as such, we recommend that any build using Cake.Recipe also targets using 2.3.0 of Cake. We recommend that you follow the [upgrade instructions for Cake itself](https://cakebuild.net/docs/getting-started/upgrade#cake-1.x-to-cake-2.0), to ensure that there aren't any additional changes that you would need to make.
+Cake.Recipe is now using 2.3.0 of Cake, and as such, we recommend that any build using Cake.Recipe also targets using 2.3.0 of Cake. We recommend that you follow the [upgrade instructions for Cake itself](https://cakebuild.net/docs/getting-started/upgrade#cake-1.x-to-cake-2.0), to ensure that there aren't any additional changes that you would need to make.
+
+### Ensure correct Cake.Issues.Recipe usage
+
+In this release of Cake.Recipe we have upgraded to 2.0.0 of Cake.Issues.Recipe. If in your build scripts you have extended the built in usage of Cake.Issues.Recipe you may need to check the release notes to confirm if there are any additional changes that need to be made.
+
+[Check out the blog post here for additional information](https://cakeissues.net/news/cake-issues-v2.0.0-released).