Update pull_request_template.md

Contribution agreement

Author: teon

.github/pull_request_template.md

@@ -1,3 +1,9 @@
+## 📝 New contributors 
+
+- [ ] I have read, understand, and agree to the Contributor Agreement. By checking this box, I confirm I have the right to contribute this work and I grant Defguard sp. z o.o. the necessary rights to use my contribution as outlined in the full agreement.: (https://tnt.sh/s/defguard-contribution-agreement)[https://tnt.sh/s/defguard-contribution-agreement]
+
+⚠︎ If the checkbox will not be confirmed - we can't include your contribution in our codebase.
+
 ## 📖 Description
 
 1. include a **summary of the changes and the related issue**, eg. _Closes #XYZ_