Beta 2 of Margen fixes a usability bug and adds helpful features.

Fixed the modified timestamp bug. Before, every time you opened a note
to read it, it would save with modificada=now and jump to the top of the
sidebar list. Now there is a dirty flag that tracks whether you actually
changed anything. Opening a note to read it does not mark it as
modified. The sidebar list stays stable when you are just browsing.

Added a markdown cheat sheet. A ? button in the sidebar opens a floating
panel with the full syntax: headers, bold, italic, lists, code blocks,
links, images, blockquotes, horizontal rules. Useful for when you forget
how to do something without leaving the editor.

Also added a welcome note that appears on first launch with examples of
every markdown feature rendered in the preview. You can delete it if you
want.

Changed the typography from Source Serif 4 to Bitter, a slab serif that
gives a more typewriter feel without being monospaced. Still legible,
but more character.
I personally like this version, this is like, the base of what i want to build, i would leave it like this and thats it, but I feel that i can get better at coding if i just add more things, it would be more usefull