Simplify web deployment notes

Readme.md

@@ -68,6 +68,27 @@ npm start
 Note: you do not need to run `npm install` every time.
 Next time you can simply run `npm start` only. 
 
+###### Deploying on a web server ######
+
+The browser version requires a server-side setup in addition to the static
+HTML/JavaScript files.
+
+In particular:
+
+* the browser build uses `TrimSPweb.js` rather than the Electron-specific
+  `TrimSPelec.js`
+* the simulation backend must be available on the server
+* a web-exposed helper/CGI layer is required to create input files, run the
+  backend, and return the generated output
+
+Notes:
+
+* this repository does not currently include the CGI/backend helper used by
+  the online deployment
+* a plain static web server is therefore not sufficient for running web
+  simulations from this checkout
+* static hosting can still be used to test page loading only
+
 ### Contact ###
 
 Zaher Salman <zaher.salman@psi.ch>