Add gemspec to be able to publish common lib files as a gem

Add gemspec to be able to publish common lib files as a gem

diff --git a/Gemfile b/Gemfile
new file mode 100644
index 0000000..50868ba
--- /dev/null
+++ b/Gemfile
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+source 'https://rubygems.org'
+
+# Specify your gem's dependencies in onebox.gemspec
+gemspec
+
diff --git a/Gemfile.lock b/Gemfile.lock
new file mode 100644
index 0000000..3e4e74f
--- /dev/null
+++ b/Gemfile.lock
@@ -0,0 +1,23 @@
+PATH
+  remote: .
+  specs:
+    discourse_mail_receiver (1.0.0)
+      mail (~> 2.7.1)
+
+GEM
+  remote: https://rubygems.org/
+  specs:
+    mail (2.7.1)
+      mini_mime (>= 0.1.1)
+    mini_mime (1.0.2)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  bundler (~> 2.0)
+  discourse_mail_receiver!
+  mail (~> 2.7.1)
+
+BUNDLED WITH
+   2.1.4
diff --git a/discourse_mail_receiver.gemspec b/discourse_mail_receiver.gemspec
new file mode 100644
index 0000000..5d9d7a2
--- /dev/null
+++ b/discourse_mail_receiver.gemspec
@@ -0,0 +1,24 @@
+# frozen-string-literal: true
+
+# coding: utf-8
+lib = File.expand_path('../lib', __FILE__)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
+
+Gem::Specification.new do |spec|
+  spec.name          = 'discourse_mail_receiver'
+  spec.version       = '1.0.0'
+  spec.authors       = ['Discourse Team']
+  spec.email         = ['team@discourse.org']
+  spec.description   = %q{A gem used to package the core .rb files of the mail-receiver.}
+  spec.summary       = spec.description
+  spec.homepage      = 'https://github.com/discourse/mail-receiver'
+  spec.license       = 'MIT'
+
+  spec.files         = Dir['lib/**/*.rb']
+  spec.require_paths = ['lib']
+
+  spec.add_runtime_dependency 'mail', '~> 2.7.1'
+  spec.add_development_dependency 'mail', '~> 2.7.1'
+  spec.add_development_dependency 'bundler', '~> 2.0'
+  spec.required_ruby_version = '>=2.4.0'
+end

GitHub sha: f02369ea