Add vendor directory and update vendorHash to null

vendor/github.com/jackc/pgx/v5/Rakefile

@@ -0,0 +1,18 @@
+require "erb"
+
+rule '.go' => '.go.erb' do |task|
+  erb = ERB.new(File.read(task.source))
+  File.write(task.name, "// Code generated from #{task.source}. DO NOT EDIT.\n\n" + erb.result(binding))
+  sh "goimports", "-w", task.name
+end
+
+generated_code_files = [
+  "pgtype/int.go",
+  "pgtype/int_test.go",
+  "pgtype/integration_benchmark_test.go",
+  "pgtype/zeronull/int.go",
+  "pgtype/zeronull/int_test.go"
+]
+
+desc "Generate code"
+task generate: generated_code_files