Enable Drag and Drop on Adding Plugin Upload

A WordPress plugin that adds drag and drop capabilities to the plugin upload form on /wp-admin/plugin-install.php.

Features:

• Drag and drop ZIP files directly onto the upload form
• Visual feedback during drag operations
• Click-to-browse functionality on the drop zone
• Automatic file validation (ZIP files only)
• Success/error messages for user feedback
• Smooth animations and transitions

How It Works:

The plug-in:
* Only loads on the plug-in install page (plugin-install.php)
* Adds a visual drop zone below the upload form
* Handles drag and drop events
* Validates dropped files (must be ZIP files)
* Automatically populates the file input when a file is dropped
* Provides visual feedback during drag operations

Browser Support:

Works in all modern browsers that support the HTML5 Drag and Drop API:
* Chrome
* Firefox
* Safari
* Edge