📘 doc: add @fedify/elysia (#593)

Author: dodok8

docs/plugins/overview.md

@@ -116,6 +116,7 @@ This is to ensure developers end up with a performant web server they intend to
 -   [Elysia Remote DTS](https://github.com/rayriffy/elysia-remote-dts) - A plugin that provide .d.ts types remotely for Eden Treaty to consume.
 -   [Cap Checkpoint plugin for Elysia](https://capjs.js.org/guide/middleware/elysia.html) - Cloudflare-like middleware for Cap, a lightweight, modern open-source CAPTCHA alternative designed using SHA-256 PoW.
 -   [Elysia Background](https://github.com/staciax/elysia-background) - A background task processing plugin for Elysia.js
+-   [@fedify/elysia](https://github.com/fedify-dev/fedify/tree/main/packages/elysia) - A plugin that provides seamless integration with [Fedify](https://fedify.dev/), the ActivityPub server framework.
 
 ## Complementary projects: