Add "Supported by" section to README.md

Author: nakamura-to

README.md

@@ -15,6 +15,11 @@ Doma has various strengths:
 [![project chat](https://img.shields.io/badge/zulip-join_chat-green.svg)](https://domaframework.zulipchat.com)
 [![Twitter](https://img.shields.io/badge/[email protected]?style=flat)](https://twitter.com/domaframework)
 
+### Supported by
+[![JetBrains logo.](https://resources.jetbrains.com/storage/products/company/brand/logos/jetbrains.svg)](https://jb.gg/OpenSourceSupport)
+
+---
+
 Prerequisite
 ---------------------