Add Hadolint - Haskell Dockerfile Linter

[PeterDaveHello]

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Hello, I'd like to know if we can add the most popular Dockerfile linter on Travis CI?

So that we can easily lint Dockerfile without any additional works but just focus on the lint result!

Here's its GitHub repository 👉 https://github.com/hadolint/hadolint/

I've prepared a simple patch for it as below and ready to send a pull request if you'd like to accept it!

Please let me know what do you think, thanks!

diff --git a/cookbooks/travis_build_environment/attributes/default.rb b/cookbooks/travis_build_environment/attributes/default.rb
index 895f2a2..48405f4 100644
--- a/cookbooks/travis_build_environment/attributes/default.rb
+++ b/cookbooks/travis_build_environment/attributes/default.rb
@@ -225,6 +225,9 @@ default['travis_build_environment']['gimme']['install_user'] = 'travis'
 default['travis_build_environment']['gimme']['install_user_home'] = '/home/travis'
 default['travis_build_environment']['gimme']['debug'] = false
 
+default['travis_build_environment']['hadolint_url'] = 'https://github.com/hadolint/hadolint/releases/download/v2.5.0/hadolint-Linux-x86_64'
+default['travis_build_environment']['hadolint_checksum'] = '6666cb1a002d71652c9972bcd3e5e100f65ea019c68c1a05b9428a8444d6f8f3'
+
 default['travis_build_environment']['haskell']['ghc_versions'] = %w[
   8.6.1
 ]
diff --git a/cookbooks/travis_build_environment/recipes/basic.rb b/cookbooks/travis_build_environment/recipes/basic.rb
index d38f10c..e0bac9d 100644
--- a/cookbooks/travis_build_environment/recipes/basic.rb
+++ b/cookbooks/travis_build_environment/recipes/basic.rb
@@ -76,6 +76,7 @@ end
 include_recipe 'travis_build_environment::yarn'
 include_recipe 'travis_build_environment::shellcheck'
 include_recipe 'travis_build_environment::shfmt'
+include_recipe 'travis_build_environment::hadolint'
 include_recipe 'travis_build_environment::mercurial'
 include_recipe 'travis_build_environment::locale'
 include_recipe 'travis_build_environment::hostname'
diff --git a/cookbooks/travis_build_environment/recipes/hadolint.rb b/cookbooks/travis_build_environment/recipes/hadolint.rb
new file mode 100644
index 0000000..79eae75
--- /dev/null
+++ b/cookbooks/travis_build_environment/recipes/hadolint.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+remote_file '/usr/local/bin/hadolint' do
+  source node['travis_build_environment']['hadolint_url']
+  checksum node['travis_build_environment']['hadolint_checksum']
+  owner node['travis_build_environment']['user']
+  group node['travis_build_environment']['group']
+  mode 0o755
+  not_if { node['kernel']['machine'] == 'ppc64le' }
+end