docs: add README for setup and usage

Author: sakethpathike

README.md

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+# Linkora Browser Extension
+
+Browser extension that adds "Share from other app" functionality to web browsers. Integrates with your Linkora Sync-Server to save and sync web page links with metadata.
+
+## Quick Start
+
+### Prerequisites
+Ensure your Linkora Sync-Server is running and accessible.
+
+### Installation
+The extension is not yet available on official web stores. Manual installation is required:
+
+1. **Download**: Get the latest release from the [Linkora Browser Extension Releases](https://github.com/linkora/browser-extension/releases) page
+
+2. **Extract**: Unzip the downloaded file to a dedicated folder
+
+3. **Load Extension**:
+
+   **Chromium-based browsers** (Chrome, Brave, Edge):
+   - Navigate to `chrome://extensions` (or `brave://extensions`, `edge://extensions`)
+   - Enable "Developer mode"
+   - Click "Load unpacked" and select the extracted folder
+
+   **Firefox**:
+   - Go to `about:debugging#/runtime/this-firefox`
+   - Click "Load Temporary Add-on..." and select `manifest.json` from the extracted folder
+   - *Note*: Firefox requires reloading the extension after each browser restart
+
+### Configuration
+After installation:
+
+1. Click the Linkora icon in your browser toolbar
+2. Enter your Linkora Sync-Server URL (e.g., `https://YOUR_SERVER_IP:PORT`)
+3. Provide the `serverAuthToken` configured on your Sync-Server
+
+### HTTPS Certificate Setup (Important)
+For HTTPS functionality, proper certificate configuration is required:
+
+**Chromium-based Browsers**: Import the certificate (`.pem` file) generated by your Sync-Server into your browser's trusted root certification authorities.
+
+**Firefox**: Go to `about:preferences#privacy` → "View Certificates" → "Servers" and add your server URL with port.
+
+## Compatibility
+
+### Server Requirements
+Requires a running Linkora Sync-Server instance. The server provides the UI components and handles synchronization logic.
+
+*Future Update*: Direct communication with the Linkora desktop app will be supported in an upcoming release.
+
+### Browser Support
+**Tested**: Firefox and Brave
+
+**Known Issues**: Zen browser (Firefox-based) experiences crashes during extension loading.
+
+## Features
+
+**Web Content Capture**: Saves web page metadata (URL, title, image) with optional notes into chosen folders. Replicates the mobile app's "Share from other app" workflow for desktop browsers.
+
+**Sync-Server Integration**: Connects to your self-hosted Linkora Sync-Server for synchronization across devices.
+
+**Hybrid Architecture**: Server-rendered UI with client-side browser operations.
+
+## Screenshots
+| | | | |
+|---|---|---|---|
+| ![](assets/1.png) | ![](assets/2.png) | ![](assets/3.png) | ![](assets/4.png) |
+
+Clicking on the folder name (in the last image) will save the link into that folder.
+
+## Support
+**Star the repo** if you find Linkora useful
+
+[![ko-fi](https://ko-fi.com/img/githubbutton_sm.svg)](https://ko-fi.com/sakethpathike)
+
+## License
+This extension is licensed under the MIT License.