Add rake task for generating AUTHORS.md (#8661)

* add rake task for generating AUTHORS.md

* update AUTHORS.md

* rubocop

lib/tasks/repo.rake

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+namespace :repo do
+  desc 'Generate the authors.md file'
+  task :authors do
+    file = File.open('AUTHORS.md', 'w')
+    file << <<~HEADER
+      Mastodon is available on [GitHub](https://github.com/tootsuite/mastodon)
+      and provided thanks to the work of the following contributors:
+
+    HEADER
+
+    url = 'https://api.github.com/repos/tootsuite/mastodon/contributors?anon=1'
+    HttpLog.config.compact_log = true
+    while url.present?
+      response = HTTP.get(url)
+      contributors = Oj.load(response.body)
+      contributors.each do |c|
+        file << "* [#{c['login']}](#{c['html_url']})\n" if c['login']
+        file << "* [#{c['name']}](#{c['email']})\n" if c['name']
+      end
+      url = LinkHeader.parse(response.headers['Link']).find_link(%w(rel next))&.href
+    end
+
+    file << <<~FOOTER
+
+      This document is provided for informational purposes only. Since it is only updated once per release, the version you are looking at may be currently out of date. To see the full list of contributors, consider looking at the [git history](https://github.com/tootsuite/mastodon/graphs/contributors) instead.
+    FOOTER
+  end
+end