Added PR readiness checklist.

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,9 +1,11 @@
-<!-- Please use this line to close one or multiple issues when this pullrequest gets merged
+### Pull Request Readiness Checklist
-You can add another line right under the first one:
-resolves #1234
-resolves #1235
--->
 
-### This pullrequest changes
+See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
 
-<!-- Please describe what your pullrequest is changing -->
+- [ ] I agree to contribute to the project under OpenCV (BSD) License.
+- [ ] To the best of my knowledge, the proposed patch is not based on a code under GPL or other license that is incompatible with OpenCV
+- [ ] The PR is proposed to proper branch
+- [ ] There is reference to original bug report and related work
+- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
+      Patch to opencv_extra has the same branch name.
+- [ ] The feature is well documented and sample code can be built with the project CMake