Avoid warning about Ruby 3.5

warning: logger was loaded from the standard library, but will no longer be part of the default gems since Ruby 3.5.0. Add logger to your Gemfile or gemspec.

excel-esv.gemspec

@@ -17,4 +17,5 @@ Gem::Specification.new do |spec|
   spec.require_paths = [ "lib" ]
 
   spec.add_dependency "spreadsheet"
+  spec.add_runtime_dependency "logger"
 end