UI and styling update?

[lucasod3v]

Hi there!

I've been using WLED for a while and thought I'd contribute. Below are the details of my suggestion:

Description:

• This PR introduces a minor change to styling and UI.
• Implemented using TailwindCSS (I hope this is okay).

Testing:

• Tested on an ESP32 and confirmed flashing works as expected. *I have not done thorough testing, for due diligence test with other kind of boards such as sound reactive and ethernet, just in case. AFAIK this shouldn't change any of the actual behavior of the installer.
• Note: v2.html has not been tested.

Visual Changes:

I've included images to showcase the changes:

Additional Notes:

The background color can be reverted to the original if needed.