Only 'commit' code files

When creating the example repo in azure devops, non-code files
sometimes start with non-standard characters (e.g. a BOM character).

As a result we are unable to successfully JSON encode the body to create
the repo, resulting in the setup script erroring out.

azure_devops/bootstrap/setup

@@ -92,7 +92,7 @@ def create_repository(options)
     }],
     commits: [{
       comment: "Initial commit.",
-      changes: Dir[File.join(tmp_dir, "**/*")].reject {|f| File.directory?(f) }.map do |entry|
+      changes: Dir[File.join(tmp_dir, "**/*.{cs,csproj,sln}")].reject {|f| File.directory?(f) }.map do |entry|
         {
           changeType: "add",
           item: {