fix: exclude some files from published gem (#108)

Co-authored-by: Takashi Kokubun <takashikkbn@gmail.com>

Author: G-Rath

erb.gemspec

@@ -20,8 +20,8 @@ Gem::Specification.new do |spec|
   spec.metadata['source_code_uri'] = spec.homepage
   spec.metadata['changelog_uri'] = "https://github.com/ruby/erb/blob/v#{spec.version}/NEWS.md"
 
-  spec.files         = Dir.chdir(File.expand_path('..', __FILE__)) do
-    `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|spec|features)/}) }
+  spec.files = Dir.chdir(__dir__) do
+    `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|\.git|\.github)/}) }
   end
   spec.bindir        = 'libexec'
   spec.executables   = ['erb']