Add DCO (#978)

Add developer certificate of origin

.github/PULL_REQUEST_TEMPLATE/pull_request_template.md

@@ -0,0 +1,7 @@
+## Description:
+
+
+## Checklist:
+  - [ ] The pull request is done against the latest development branch
+  - [ ] Only one feature/fix was added per PR and the code change compiles without warnings
+  - [ ] I accept the [DCO](https://github.com/1technophile/OpenMQTTGateway/blob/development/docs/participate/development.md#developer-certificate-of-origin).

docs/participate/development.md

@@ -33,3 +33,37 @@ Some things that will increase the chance that your pull request is accepted:
 * Write a [good commit message][commit].
 
 [commit]: http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html
+
+## Developer Certificate Of Origin
+
+```
+    By making a contribution to this project, I certify that:
+
+    (a) The contribution was created in whole or in part by me and I
+        have the right to submit it under the open source license
+        indicated in the file; or
+
+    (b) The contribution is based upon previous work that, to the best
+        of my knowledge, is covered under an appropriate open source
+        license and I have the right under that license to submit that
+        work with modifications, whether created in whole or in part
+        by me, under the same open source license (unless I am
+        permitted to submit under a different license), as indicated
+        in the file; or
+
+    (c) The contribution was provided directly to me by some other
+        person who certified (a), (b) or (c) and I have not modified
+        it.
+
+    (d) I understand and agree that this project and the contribution
+        are public and that a record of the contribution (including all
+        personal information I submit with it, including my sign-off) is
+        maintained indefinitely and may be redistributed consistent with
+        this project or the open source license(s) involved.
+```
+
+This Developer Certificate Of Origin (DCO) was adopted on June 7, 2021.
+
+The text of this license is available under the [Creative Commons Attribution-ShareAlike 3.0 Unported License](http://creativecommons.org/licenses/by-sa/3.0/).  It is based on the Linux [Developer Certificate Of Origin](http://elinux.org/Developer_Certificate_Of_Origin).
+
+To accept the DCO it is required to put a x between [ ] on `[ ] I accept the DCO` in the PR template when submitting it. The [ ] is an opt-in box, so you have to manually accept it.