Issue 4931 - add possibility to not send data depending on connection properties

README.md

 libadblockplus
 ==============
 
 A C++ library offering the core functionality of Adblock Plus.
 
 Getting/updating the dependencies
 ---------------------------------
 
 libadblockplus has dependencies that aren't part of this repository. They are
 retrieved and updated during the build process, but you can also manually update
@@ skipping 202 matching lines @@
 done via a second type of filter that is completely ignored when matching URLs:
 [element hiding rules](https://adblockplus.org/en/filters#elemhide).
 
 You can retrieve a list of all CSS selectors for elements that should be hidden
 using
 [`FilterEngine::GetElementHidingSelectors`](https://adblockplus.org/docs/libadblockplus/class_adblock_plus_1_1_filter_engine.html#a91c44dac13c7655230be49440f45a168).
 
 What libadblockplus clients typically do with this is to generate a CSS style
 sheet that is injected into each page.
 
+### Disabling network requests from Adblock Plus on current connection
+At any moment you can call [`FilterEngine::SetAllowedConnectionType`](https://adblockplus.org/docs/libadblockplus/class_adblock_plus_1_1_filter_engine.html#a4bee602fb50abcb945d3f19468fd8893) to change the settings indicating what connection types are allowed in your application. However to have it working you should also pass a callback function into factory method of FilterEngine. This callback is being called before each request and the value of argument is earlier passed string into `FilterEngine::SetAllowedConnectionType`, what allows to query the system and check whether the current connection is in accordance with earlier stored value in settings.
+For example, you can pass "not_metered" into [`FilterEngine::SetAllowedConnectionType`](https://adblockplus.org/docs/libadblockplus/class_adblock_plus_1_1_filter_engine.html#a4bee602fb50abcb945d3f19468fd8893) and on each request you can check whether the current connection is "not_metered" and return true or false from you implementation of callback [`AdblockPlus::FilterEngine::CreateParameters::isConnectionAllowed`](https://adblockplus.org/docs/libadblockplus/structAdblockPlus_1_1FilterEngine_1_1CreateParameters.html#a86f427300972d3f98bb6d4108301a526).
+
 Shell
 -----
 
 The _shell_ subdirectory contains an example application using libadblockplus.
 
 It's a simple shell that loads subscriptions into memory and checks
 whether a specified resource would be blocked or not.
 
 To see the available commands, type `help`.
 
 ### Unix
 
 The shell is automatically built by `make`, you can run it as follows:
 
     build/out/abpshell
 
 ### Windows
 
 Just run the project *abpshell*.