Add paket files to .gitignore.

Author: criemen

csharp/.gitignore

@@ -14,4 +14,5 @@ csharp.log
 .vscode/launch.json
 
 extractor/Semmle.Extraction.CSharp.Driver/Properties/launchSettings.json
-extractor-pack
+extractor-pack
+paket-files/