Identify config.ru rackup file as ruby

Author: mmlb

identify/extensions.py

@@ -326,6 +326,7 @@
     'BUILD.bazel': EXTENSIONS['bzl'],
     'CMakeLists.txt': EXTENSIONS['cmake'],
     'CHANGELOG': EXTENSIONS['txt'],
+    'config.ru': EXTENSIONS['rb'],
     'CONTRIBUTING': EXTENSIONS['txt'],
     'COPYING': EXTENSIONS['txt'],
     'Dockerfile': {'text', 'dockerfile'},

tests/identify_test.py

@@ -160,6 +160,7 @@ def test_tags_from_path_plist_text(tmpdir):
         ('Pipfile.lock', {'text', 'json'}),
         ('mod/test.py', {'text', 'python'}),
         ('mod/Dockerfile', {'text', 'dockerfile'}),
+        ('config.ru', {'text', 'ruby'}),
         ('Gemfile', {'text', 'ruby'}),
         ('Gemfile.lock', {'text'}),
         ('Jenkinsfile', {'text', 'groovy', 'jenkins'}),