add issue and pull request template

.github/ISSUE_TEMPLATE.md

+<!--
+If you have a question rather than reporting a bug please go to http://answers.opencv.org where you get much faster responses.
+If you need further assistance please read [How To Contribute](https://github.com/Itseez/opencv/wiki/How_to_contribute).
+
+This is a template helping you to create an issue which can be processed as quickly as possible. This is the bug reporting section for the OpenCV library.
+-->
+
+##### System information (version)
+<!-- Example
+- OpenCV => 3.1
+- Operating System / Platform => Windows 64 Bit
+- Compiler => Visual Studio 2015
+-->
+
+- OpenCV => :grey_question:
+- Operating System / Platform => :grey_question:
+- Compiler => :grey_question:
+
+##### Detailed description
+
+<!-- your description -->
+
+##### Steps to reproduce
+
+<!-- to add code example fence it with triple backticks and optional file extension
+    ```.cpp
+    // C++ code example
+    ```
+ or attach as .txt or .zip file
+-->
\ No newline at end of file

.github/PULL_REQUEST_TEMPLATE.md

+<!-- Please use this line to close one or multiple issues when this pullrequest gets merged
+You can add another line right under the first one:
+resolves #1234
+resolves #1235
+-->
+
+### This pullrequest changes
+
+<!-- Please describe what your pullrequest is changing -->