Merge pull request #2441 from asmorkalov:pr_template

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### Pull Request Readiness Checklist

### This pullrequest changes

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

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- [ ] 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