add dark mode

[nidhi752]

Adding dark mode will enhance the user interface.
Please assign this to me under hackoctoberfest'24

[cwarnermm]

Hi @nidhi752 - Curious to know more about how you'd implement dark mode for the Mattermost Developer Documentation.

[nidhi752]

@cwarnermm

Dark Mode Implementation

Description

This issue introduces a dark mode feature to the website. The dark mode allows users to switch between light and dark themes easily, with the preference saved using localStorage to ensure it persists across sessions.

Changes Made

• HTML: Add a button for toggling between light and dark modes.
• CSS: Create styles for both light and dark modes, with smooth transitions.
• JavaScript: Implemente the logic to toggle dark mode and save user preferences using localStorage.

[cwarnermm]

@nidhi752 - Given that the developer documentation site is generated using Hugo, are there Hugo-supported options available already that could be used rather than developing dark mode support from scratch?