Fix the docs dark theme colors

[MikeAlhayek]

This pull request improves the dark mode styling for documentation by enhancing readability and ensuring consistent appearance for tables, cards, code blocks, and other components. The changes are applied across both docs/docs/css/custom.css and docs/src/css/custom.css to ensure a unified dark mode experience.

Dark mode styling improvements:

• Added specific styles for tables in dark mode, including text color, background color, and border color adjustments for better readability and visual consistency. [1] [2]
• Improved the appearance of table headers, striped rows, and bordered tables in dark mode for clarity and contrast. [1] [2]

General readability and component enhancements:

• Set readable text color for main elements (e.g., body, .main-wrapper, .theme-doc-root, and article) and ensured cards, example blocks, and standalone components inherit appropriate background and border colors in dark mode.
• Enhanced code block and highlight contrast in dark mode for better code visibility.
• Adjusted header and sub-header colors in dark mode to maintain sufficient contrast and visual hierarchy.