Display only current note and its relations

[yajo]

I'd love to have a sidebar similar to Obsidian's help here.

As you can see, it contains only the current node and its direct relations:

When you click on the highlighted icon, it opens the full graph in a modal (also requested in #25).

This seems to me a much better UX because:

• In a small widget, you can still get important and usable information.
• You can get the whole guacamole without having to shrink the note editor. Notes must be the protagonists in Joplin, not the graph.