feat: add window management, shortcuts, and build fixes

- Add Ctrl+Shift+N shortcut to create new windows
- Implement window state persistence (save/restore position and size)
- New windows duplicate the size of the currently focused window with an offset
- Fix Debian package chrome-sandbox permissions via after-install script
- Update build configuration: remove rpm, add author email

README.md

@@ -11,9 +11,20 @@ A linux port of <a href="https://linear.app/">linear.app</a>
 </p>
 
 # Install
+Requires `sudo` (for sandbox helper, desktop entry, and icons).
+
 ```bash
 wget -qO- https://raw.githubusercontent.com/kleo-dev/linear-linux/refs/heads/master/installer.sh | bash
 ```
 
+The installer:
+- Downloads the AppImage, extracts it under `/opt/linear-linux-<version>`, and wires up the `chrome-sandbox` helper correctly.
+- Installs a wrapper at `/usr/local/bin/linear`, a desktop entry, and the Linear icon into the system icon cache.
+- Accepts overrides: `VERSION=0.2.1 APPIMAGE_URL=<url> INSTALL_ROOT=/opt ./installer.sh`
+
+Development:
+- `npm start` launches Electron with sandbox disabled for local runs (packaged builds use the proper setuid helper).
+- `npm run build` produces an AppImage that bundles the Linear brand assets for the desktop icon.
+
 # Having an issue?
 Describe your issue [here](https://github.com/kleo-dev/linear-linux/issues)