feat: add custom appveyor file

Author: tngraf

appveyor.yml

@@ -0,0 +1,17 @@
+version: 1.0.{build}
+image: Visual Studio 2019
+install:
+  - call "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\Tools\VsDevCmd.bat"
+platform:
+  - Win32
+  - x64
+configuration:
+  - Debug
+  - Release
+cache:
+  - packages -> **\packages.config
+before_build:
+  - cmd: nuget restore
+  - project: Fossology.Rest.Dotnet.sln
+build:
+  verbosity: minimal