Add DCO content to CONTRIBUTING.md (#1460)

* Update CHANGELOG.md
Signed-off-by: NLutkin Wang <lu.wang@zilliz.com>

* Update INSTALL.md
Signed-off-by: NLutkin Wang <lu.wang@zilliz.com>

* Update INSTALL.md
Signed-off-by: NLutkin Wang <lu.wang@zilliz.com>

* Update CONTRIBUTING.md

Add DCO rules.
Signed-off-by: NLutkin Wang <lu.wang@zilliz.com>

* Update CHANGELOG.md
Signed-off-by: NLutkin Wang <lu.wang@zilliz.com>

* Update CONTRIBUTING.md
Signed-off-by: NLutkin Wang <lu.wang@zilliz.com>
Co-authored-by: NJin Hai <hai.jin@zilliz.com>

CHANGELOG.md

@@ -59,9 +59,9 @@ Please mark all change in change log and use the issue from GitHub
 - \#1002 - Rename minio to s3 in Storage Config section
 - \#1078 - Move 'insert_buffer_size' to Cache Config section
 - \#1105 - Error message is not clear when creating IVFSQ8H index without gpu resources
+- \#740, #849, #878, #972, #1033, #1161, #1173, #1199, #1190, #1223, #1222, #1257, #1264, #1269, #1164, #1303, #1304, #1324, #1388, #1459 - Various fixes and improvements for Milvus documentation.
 - \#1297 - Hide partition_name parameter, avid user directly access partition table
 - \#1310 - Add default partition tag for a table
-- \#740, #849, #878, #972, #1033, #1161, #1173, #1199, #1190, #1223, #1222, #1257, #1264, #1269, #1164, #1303, #1304, #1324, #1388 - Various fixes and improvements for Milvus documentation.
 - \#1234 - Do S3 server validation check when Milvus startup
 - \#1263 - Allow system conf modifiable and some take effect directly
 - \#1320 - Remove debug logging from faiss

CONTRIBUTING.md

@@ -58,6 +58,23 @@ Before sending your pull requests for review, make sure your changes are consist
 - Keep API compatibility in mind when you change code in Milvus. Reviewers of your pull request will comment on any API compatibility issues.
 - When you contribute a new feature to Milvus, the maintenance burden is (by default) transferred to the Milvus team. This means that the benefit of the contribution must be compared against the cost of maintaining the feature.
 
+### Developer Certificate of Origin (DCO)
+
+All contributions to this project must be accompanied by acknowledgment of, and agreement to, the [Developer Certificate of Origin](https://developercertificate.org/). Acknowledgment of and agreement to the Developer Certificate of Origin _must_ be included in the comment section of each contribution and _must_ take the form of `Signed-off-by: {{Full Name}} <{{email address}}>` (without the `{}`). Contributions without this acknowledgment will be required to add it before being accepted. If contributors are unable or unwilling to agree to the Developer Certificate of Origin, their contribution will not be included.
+
+Contributors sign-off that they adhere to DCO by adding the following Signed-off-by line to commit messages:
+
+```text
+This is my commit message
+
+Signed-off-by: Random J Developer <random@developer.example.org>
+```
+
+Git also has a `-s` command line option to append this automatically to your commit message:
+
+```shell
+$ git commit -s -m 'This is my commit message'
+```
 
 ## Coding Style
 The coding style used in Milvus generally follow [Google C++ Style Guide](https://google.github.io/styleguide/cppguide.html).