Update demo readme

demo/README.md

@@ -1,2 +1,37 @@
-To test effect of limits run: `rake demo:limits`
-To change simulation see `Rakefile`
+This is a demo rails app with a configured sidekiq-limit_fetch.
+
+Its purpose is to check whether plugin works in certain situations.
+
+Application is preconfigured with two workers:
+- app/workers/fast_worker.rb which does `sleep 0.2`
+- app/workers/slow_worker.rb which does `sleep 1`
+
+There is also a rake task which can be invoked as `bundle exec rake demo:limit`:
+
+- it prefills sidekiq tasks
+
+```ruby
+  100.times do
+    SlowWorker.perform_async
+    FastWorker.perform_async
+  end
+```
+- sets sidekiq config
+
+```yaml
+  :verbose: false
+  :concurrency: 4
+  :queues:
+    - slow
+    - fast
+  :limits:
+    slow: 1
+```
+
+- and launches a sidekiq admin page with overview of queues in browser.
+The page is set to live-poll so effects of limits can be seen directly.
+
+
+To change simulation modify `Rakefile` or workers.
+
+Any bugs related to the plugin should be demonstrated with a reproduction from this base app.