Added instructions on using BUILD_EXAMPLES=ON to build the samples

README.md

@@ -31,6 +31,8 @@ use CMake's `BUILD_opencv_*` options. Like in this example:
 $ cmake -DOPENCV_EXTRA_MODULES_PATH=<opencv_contrib>/modules -DBUILD_opencv_legacy=OFF <opencv_source_directory>
 ```
 
+If you also want to build the samples from the "samples" folder of each module, also include the "-DBUILD_EXAMPLES=ON" option.
+
 If you prefer using the gui version of cmake (cmake-gui), then, you can add `opencv_contrib` modules within `opencv` core by doing the following:
 
 1. start cmake-gui