Add the Linux Foundation's Developer Certificate of Origin in pull request template (#1022)

Author: cliu123

.github/pull_request_template.md

@@ -31,9 +31,32 @@ _Please provide as much details as possible to get feedback/acceptance on your P
 
 
 
- 8. __Is it backport from master branch?__ (_If yes, please add backport PR # and commits #_)
+ 8. __Is it backport from main branch?__ (_If yes, please add backport PR # and commits #_)
 
 
 
 
-By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.
+
+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.