fix(pwa): serve manifest for html accept headers (#1828)

* fix(pwa): serve manifest for html accept headers

* style: add trailing newline to pwa controller

test/controllers/pwa_controller_test.rb

@@ -0,0 +1,11 @@
+require "test_helper"
+
+class PwaControllerTest < ActionDispatch::IntegrationTest
+  test "manifest responds successfully for html accept headers" do
+    get "/manifest", headers: { "Accept" => "text/html" }
+
+    assert_response :success
+    assert_equal "application/manifest+json", response.media_type
+    assert_includes response.body, '"start_url": "/"'
+  end
+end