UX Improvements / Allow fix for deleting single node

[itsonlyjames]

Love the plugin @Quorafind, certainly an awesome way to improve the usage of Canvas.

I've made some improvements to my own local copy of the plugin, and thought they'd benefit other users.

Notable changes:

• Enter now enters edit mode (space still does also)
• Meta + Enter exits edit mode (both similar to excalidraw)
• Meta + Enter now allows for fast chaining of brother node (Enter to edit node, cmd+enter to exit edit, cmd+enter again to create another brother node)
• Add setting for delete auto layout (this might be considered a bug, this function prevents deletion of a single node)

Keen to hear your thoughts on these UX improvements and if there's anything you'd do differently and/or like me to change.

This issue will be fixed with this PR.

Fixes https://github.com/Quorafind/Obsidian-Canvas-MindMap/issues/51 and https://github.com/Quorafind/Obsidian-Canvas-MindMap/issues/48