Add ADOPTERS file

ADOPTERS.md

@@ -0,0 +1,21 @@
+# Adopters
+
+This list represents the collection of organizations that are using PipeCD within their environments. If
+you are currently utilizing PipeCD and not yet on this list, we strongly encourage you to add your organization
+here as well!
+
+The objective of this list is to serve as a comprehensive and authoritative resource for the entire PipeCD adopter community, while also inspiring those who are embarking on their PipeCD journey.
+
+Contributing to this list may seem like a small effort, but it has a **big impact** on the growth, maturity, and momentum of the project. We extend our gratitude to all the adopters and contributors of the PipeCD project!
+
+## Updating this list
+
+To add your organization to this list, open a PR to update this list.
+
+## PipeCD Adopters
+
+This list is arranged in the order of organizations being added to it.
+
+| Organization | Contact | Description of Use |
+| --- | --- | --- |
+| [CyberAgent, Inc.](https://www.cyberagent.co.jp/) | @kentakozuka | PipeCD is used as an internal CD infrastructure, supporting over 20 projects. About 80 active piped agents are deploying about 2,900 applications in all dev, staging, and production environments. |

README.md

@@ -76,6 +76,12 @@ As a CNCF Sandbox project, PipeCD follows [CNCF Code of Conduct](https://github.
 
 #
 
+### Adopters
+
+You can find a list of publicly recognized users of the PipeCD in the (ADOPTERS.md)[ADOPTERS.md] file. We strongly encourage all PipeCD users to add their names to this list, as we love to see the community's growing success!
+
+#
+
 ### Thanks to the contributors of PipeCD!
 
 <a href="https://github.com/nghialv"><img src="https://avatars.githubusercontent.com/u/1751755?v=4" title="nghialv" width="80" height="80"></a>