UPDATE: split the webapp in a widget and the app itself

This splits the webapp in:

* IronCalc (the widget to be published on npmjs)
* The frontend for our "service"
* Adds "dummy code" for the backend using sqlite

webapp/app.ironcalc.com/README.md

@@ -0,0 +1,44 @@
+# IronCalc service application
+
+This directory contains the code (frontend and backend) to run the code deployed at https://app.ironcalc.com
+
+## Development build:
+
+1. Run in this folder `caddy run` (that just just a proxy for the front end and backend).
+   You will need to leave it running all the time.
+2. In the server folder run `cargo run`
+3. In the frontend folder `npm install` and `npm run dev`
+
+That's it if you point your browser to localhost:2080 you should see the app.
+
+Note that step three involves alo building thw wasm bindings and the widget
+
+## Deployment
+
+The development environment is very close to a deployment environment.
+
+### Build the server binary:
+
+In the server directory run:
+
+```
+cargo build --release
+```
+
+You will find a single binary in target/release/ironcalc_server
+
+### Build the frontend files
+
+In the frontend folder:
+
+```
+npm install
+npm run build
+```
+
+That will create a bunch of files that you should copy to your server
+
+## TODO
+
+Deployment details, brotli, logs, stats, Postgres, systemctl files, ...
+