Optimize code

- Bug fixes and minor improvements

- FIX: fix crash when opening file from Files app

- NEW: Editing multiple files in one window supported

- Improve keyboard operations on iPad with Magci Keyboard
- JSON View now supports Undo and Redo operations
- Show count of children for Array and Object nodes
- Fix full version validation problem

- Improve keyboard operations on iPad with Magci Keyboard
- JSON View now supports Undo and Redo operations
- Show count of children for Array and Object nodes

- Improved JSON text editor performance
- Add keyboard toolbar for JSON text editor

- Now supports Multiple Windows, you can edit two JSON files in one screen on iPad
- Search in Text View now supports Case Sensitive option
- Replace feature added to TextView

- Add Search feature in TextView mode, keyboard shortcuts also be supported
- Cmd+F to open search panel, Cmd+G, Cmd+Shift+G to navigate previous and next search result

- Add Dark mode theme in Text View
- Fix key field text color in dark mode

- Keyboard commands support added!
- On iPad, now you can use multiple shortcuts with an external keyboard, to navigate, edit, manipulate JSON nodes in tree view
- Context menu added, with a lot JSON tree node manipulation function included

- Add Export to Pasteboard tool