Update readme

readme.md

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 [![npm](https://img.shields.io/npm/v/yomichan-dict-builder?style=for-the-badge)](https://www.npmjs.com/package/yomichan-dict-builder)
 
 This is a library for building dictionaries for
-[Yomichan](https://foosoft.net/projects/yomichan/)/[Yomitan](https://github/themoeway/yomitan)
-from scratch.
+[Yomitan](https://github/themoeway/yomitan) from scratch. Note that Yomichan is
+no longer being maintained, and thus is not compatible with some new
+dictionaries that are developed using new features exclusive to Yomitan.
 
 ## Installation