Add MangaDex-OPDS to Known Implementations

Author: rushsteve1

v1.0.md

@@ -71,6 +71,7 @@ The Link **MUST** contain the following attributes:
 - [Kavita](https://www.kavitareader.com/)
 - [Codex](https://github.com/ajslater/codex/)
 - [LANraragi](https://github.com/Difegue/LANraragi)
+- [MangaDex-OPDS](https://github.com/rushsteve1/mangadex-opds)
 
 ### Client