Update keyboard shortcuts documentation and formatting

[joerivan]

Summary

Adds a new keyboard shortcuts documentation page for Atom Architect.

Changes

• Added shortcuts.md with a structured overview of available keyboard shortcuts.

• Documented shortcuts for:

  • General actions such as opening files, saving geometry, and showing the debug log.
  • Camera alignment and camera mode controls.
  • Atom selection actions.
  • Geometry editing operations such as grab, rotate, delete, freeze, undo, and redo.
  • NEB analysis navigation.

• Included notes about panel-specific shortcut behavior and important global shortcuts such as Ctrl+Q and Ctrl+W.

Motivation

This documentation gives users a central reference for keyboard shortcuts in Atom Architect, making the editor, geometry optimization viewer, and NEB analysis workflows easier to discover and use.