Added Distribute Horizontally for cpal

[1Prototype1]

This pull request includes enhancements to the wled00/data/cpal/cpal.htm file, primarily focusing on adding a "Distribute horizontally" feature for color markers in Custom Palette Editor. It also includes minor refactoring existing code to use these new SVG definitions.

New Functionality:

• Added a "Distribute Horizontally" button to the palette editor, which allows users to distribute color markers equally across the gradient.

Code Refactoring:

• Replaced inline SVG definition for trash with SVG icons definitions for better maintainability.

[blazoncek]

Thanks. Can you provide screenshot of the outcome?

[1Prototype1]

Before (Added color markers randomly):

After clicking distribute button: