Update pull_request_template.md

.github/pull_request_template.md

@@ -1,4 +1,4 @@
-If this PR is related to coding or code translation, please **fill out the checklist** and **paste the console outputs to the PR**.
+If this PR is related to coding or code translation, please read the [contribution guideline](https://github.com/krahets/hello-algo/issues/15#issue-1464069591), fill out the checklist, and paste the console outputs to the PR.
 
 - [ ] I've tested the code and ensured the outputs are the same as the outputs of reference codes.
 - [ ] I've checked the codes (formatting, comments, indentation, file header, etc) carefully.