Remove "dangling" Web link (README.md now more detailed than before). Build set to preview1

Author: christophwille

README.md

@@ -3,9 +3,6 @@
 
 AvalonEdit is the name of the WPF-based text editor in SharpDevelop 4.x "Mirador" and beyond. It is also being used in ILSpy and many other projects.
 
-[avalonedit.net](http://avalonedit.net/)
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 Downloads
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appveyor.yml

@@ -3,7 +3,7 @@ version: '6.0.{build}'
 dotnet_csproj:
   patch: true
   file: '**\*.csproj'
-  version: '6.0-netcore3p5alpha2'
+  version: '6.0-preview1'
   assembly_version: '{version}'
   file_version: '{version}'