Add documentation

README.md

@@ -178,7 +178,7 @@ export RACK_MINI_PROFILER_PATCH_NET_HTTP="false"
 
 To generate [flamegraphs](http://samsaffron.com/archive/2013/03/19/flame-graphs-in-ruby-miniprofiler), add the [**stackprof**](https://rubygems.org/gems/stackprof) gem to your Gemfile.
 
-Then, to view the flamegraph as a direct HTML response from your request, just visit any page in your app with `?pp=flamegraph` appended to the URL.
+Then, to view the flamegraph as a direct HTML response from your request, just visit any page in your app with `?pp=flamegraph` appended to the URL, or add the header `X-Rack-Mini-Profiler` to the request with the value `flamegraph`.
 
 Conversely, if you want your regular response instead (which is specially useful for JSON and/or XHR requests), just append the `?pp=async-flamegraph` parameter to your request/fetch URL; the request will then return as normal, and the flamegraph data will be stored for later *async* viewing, both for this request and for all subsequent requests made by this page (based on the `REFERER` header). For viewing these async flamegraphs, use the 'flamegraph' link that will appear inside the MiniProfiler UI for these requests.
 

lib/mini_profiler.rb

@@ -702,6 +702,8 @@ def help(client_settings, env)
               #{make_link "flamegraph_embed", env} : a graph representing sampled activity (requires the stackprof gem), embedded resources for use on an intranet.
               #{make_link "trace-exceptions", env} : will return all the spots where your application raises exceptions
               #{make_link "analyze-memory", env} : will perform basic memory analysis of heap
+
+              All features can also be accessed by adding the X-Rack-Mini-Profiler header to the request, with any of the values above (e.g. 'X-Rack-Mini-Profiler: flamegraph')
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