add installer to build package

README.md

@@ -22,6 +22,18 @@ npm install
 npm start
 ```
 
+## Building & installing
+
+`./build.sh` produces `build/PLWL-<version>.tar.gz`: the Electron runtime with the whole app (code, renderer and bundled `files/`) packed into `electron/resources/app.asar`, plus a `plwl` launcher, a `plwl.desktop` template and `install.sh`:
+
+```bash
+tar -xzf PLWL-<version>.tar.gz
+cd PLWL
+./install.sh   # copies to ~/.local/lib/PLWL, adds ~/.local/bin/plwl + a desktop shortcut, launches the app
+# or run without installing:
+./plwl
+```
+
 ## Wine & Proton support
 
 - **System Wine** — uses the `wine` binary from PATH.