iox-eclipse-iceoryx#828 Update PR Template and Contributing.md

Updated the template to add an entry in the Changelog if you close an
issue in GitHub. Additionally added that to Contributing.md

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,6 +2,7 @@
 
 1. [ ] Code follows the coding style of [CONTRIBUTING.md][contributing]
 1. [ ] Tests follow the [best practice for testing][testing]
+1. [ ] Changelog updated [in the unreleased section][changelog]
 1. [ ] Branch follows the naming format (`iox-#123-this-is-a-branch`)
 1. [ ] Commits messages are according to this [guideline][commit-guidelines]
     - [ ] Commit messages have the issue ID (`iox-#123 commit text`)
@@ -19,6 +20,7 @@
 [eca]: http://www.eclipse.org/legal/ECA.php
 [contributing]: https://github.com/eclipse-iceoryx/iceoryx/blob/master/CONTRIBUTING.md#coding-style
 [testing]: https://github.com/eclipse-iceoryx/iceoryx/blob/master/doc/website/advanced/best-practice-for-testing.md
+[changelog]: https://github.com/eclipse-iceoryx/iceoryx/blob/master/CHANGELOG.md
 
 ## Notes for Reviewer
 <!-- Items in addition to the checklist below that the reviewer should look for -->

CONTRIBUTING.md

@@ -53,8 +53,9 @@ Please make sure you have:
 3. All branches have the following naming format: `iox-#[issue]-branch-name` e.g. `iox-#123-super-duper-feature`
 4. All commits have the following naming format: `iox-#[issue] commit message` e.g. `iox-#123 implemented super-duper feature`
 5. All commits have been signed with `git commit -s`
-6. You open your pull request towards the base branch `master`
-7. Link the pull request to the according Github issue and set the label accordingly
+6. The CHANGELOG.md is updated with the Github issue that is closed by the Pull-Request (add to unreleased section)
+7. You open your pull request towards the base branch `master`
+8. Link the pull request to the according Github issue and set the label accordingly
 
 **NOTE:** For support while developing you can use little helper scripts, see [git-hooks](https://github.com/eclipse-iceoryx/iceoryx/blob/master/tools/git-hooks/Readme.md).