Merge pull request opencv#12093 from CYTing1998:update_issue

* I have updated the requirements of reporting issues inside ISSUE_TEMPLATE.md

Author: CYTing1998

.github/ISSUE_TEMPLATE.md

@@ -2,6 +2,14 @@
 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/opencv/opencv/wiki/How_to_contribute).
 
+Please:
+
+* Read the documentation to test with the latest developer build.
+* Check if other person has already created the same issue to avoid duplicates. You can comment on it if there already is an issue.
+* Try to be as detailed as possible in your report.
+* Report only one problem per created issue.
+
+
 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.
 -->
 
@@ -27,4 +35,4 @@ This is a template helping you to create an issue which can be processed as quic
     // C++ code example
     ```
  or attach as .txt or .zip file
--->
+-->