Restore gem tzinfo-data for Windows & JRuby (cotes2020#176)

Author: cotes2020

Diff for: Gemfile

@@ -2,7 +2,7 @@ source "https://rubygems.org"
 
 gem "jekyll", ">=3.8.6"
 
-# Official Plugins
+# plugins
 group :jekyll_plugins do
   gem "jekyll-paginate"
   gem "jekyll-redirect-from"
@@ -13,3 +13,13 @@ end
 group :test do
   gem "html-proofer"
 end
+
+# Windows and JRuby does not include zoneinfo files, so bundle the tzinfo-data gem
+# and associated library.
+install_if -> { RUBY_PLATFORM =~ %r!mingw|mswin|java! } do
+  gem "tzinfo", "~> 1.2"
+  gem "tzinfo-data"
+end
+
+# Performance-booster for watching directories on Windows
+gem "wdm", "~> 0.1.1", :install_if => Gem.win_platform?