docs: add OpenCode-Obsidian plugin (#7129)

packages/web/src/content/docs/ecosystem.mdx

@@ -54,6 +54,7 @@ You can also check out [awesome-opencode](https://github.com/awesome-opencode/aw
 | [opencode.nvim](https://github.com/sudo-tee/opencode.nvim)                                 | Neovim frontend for opencode - a terminal-based AI coding agent |
 | [ai-sdk-provider-opencode-sdk](https://github.com/ben-vargas/ai-sdk-provider-opencode-sdk) | Vercel AI SDK provider for using OpenCode via @opencode-ai/sdk  |
 | [OpenChamber](https://github.com/btriapitsyn/openchamber)                                  | Web / Desktop App and VS Code Extension for OpenCode            |
+| [OpenCode-Obsidian](https://github.com/mtymek/opencode-obsidian)                           | Obsidian plugin that embedds OpenCode in Obsidian's UI          |
 
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