Add ADOPTERS file (#4460)

* Add ADOPTERS file

Signed-off-by: Kenta Kozuka <[email protected]>

* Format the file

Signed-off-by: Kenta Kozuka <[email protected]>

---------

Signed-off-by: Kenta Kozuka <[email protected]>

ADOPTERS.md

@@ -0,0 +1,19 @@
+# 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>