Redesign using MD3 system

[Rectos28]

Description

New theme system inspired by Material Design 3 and Color tokens for easier customization.

• Changed all color to MD3 color tokens system for easier theming
• Introduced new Light/Dark themes
• Changed all Tool Icon files to MD3 Icons for easier customization
• Change to all pages to adapt the new theme system.
• Change to the dark mode system
• Changed some JS files to adapt the new Icons & theme
• Updated language files with the new introduced tags

Checklist:

• I have read the Contribution Guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings

Contributor License Agreement

By submitting this pull request, I acknowledge and agree that my contributions will be included in Stirling-PDF and that they can be relicensed in the future under the MPL 2.0 (Mozilla Public License Version 2.0) license.

(This does not change the general open-source nature of Stirling-PDF, simply moving from one license to another license)