Tabs and improved UX

Short update about the app

First of all, I have noticed that file upload is not working from the embedded itch.io page. It is becaouse the CORS policy, so I have added a message to suggest using the app in its own domain

I have added a new feature, which is shortcuts. Now you can mark notes as tabs, that appear at the bottom of the screen to move faster between frequent tabs.

I have also changed when unused notes are removed. Now it only happens when a file is loaded, and not on every edit. This prevents notes from being deleted when their only reference is removed.

I have also recovered a lost functionality that made the display show the section being editted.

That is all for now!

Jose