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/frontend/src/index.css

@@ -0,0 +1,5 @@
+body {
+  inset: 0px;
+  margin: 0;
+  padding: 0;
+}