Contributor license agreement (NVIDIA#393)

* Documenting CLA and signoff requirement

Signed-off-by: Sameer Raheja <[email protected]>

* Fix typos, add links

Signed-off-by: Sameer Raheja <[email protected]>

* Fix typo

Signed-off-by: Sameer Raheja <[email protected]>

CONTRIBUTING.md

@@ -48,13 +48,77 @@ project.  For IntelliJ IDEA users, an
 
 This project follows the official
 [Scala style guide](https://docs.scala-lang.org/style/) and the
-[Databricks Scala guide](Databricks Scala guide), preferring the latter.
+[Databricks Scala guide](https://github.com/databricks/scala-style-guide), preferring the latter.
 
 #### Java
 
 This project follows the
 [Oracle Java code conventions](http://www.oracle.com/technetwork/java/codeconvtoc-136057.html)
 and the Scala conventions detailed above, preferring the latter.
 
+### Sign your work
+
+We require that all contributors sign-off on their commits. This certifies that the contribution is your original work, or you have rights to submit it under the same license, or a compatible license.
+
+Any contribution which contains commits that are not signed off will not be accepted.
+
+To sign off on a commit use the `--signoff` (or `-s`) option when committing your changes:
+
+```shell
+git commit -s -m "Add cool feature."
+```
+
+This will append the following to your commit message:
+
+```
+Signed-off-by: Your Name <[email protected]>
+```
+
+The sign-off is a simple line at the end of the explanation for the patch. Your signature certifies that you wrote the patch or otherwise have the right to pass it on as an open-source patch. Use your real name, no pseudonyms or anonymous contributions.  If you set your `user.name` and `user.email` git configs, you can sign your commit automatically with `git commit -s`.
+
+
+The signoff means you certify the below (from [developercertificate.org](https://developercertificate.org)):
+
+```
+Developer Certificate of Origin
+Version 1.1
+
+Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
+1 Letterman Drive
+Suite D4700
+San Francisco, CA, 94129
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+
+
+Developer's Certificate of Origin 1.1
+
+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.
+```
+
+
 ## Attribution
-Portions adopted from https://github.com/rapidsai/cudf/blob/main/CONTRIBUTING.md
+Portions adopted from https://github.com/rapidsai/cudf/blob/main/CONTRIBUTING.md, https://github.com/NVIDIA/nvidia-docker/blob/main/CONTRIBUTING.md, and https://github.com/NVIDIA/DALI/blob/main/CONTRIBUTING.md