I would propose something like this to start with: https://demo.sentido-labs.com...

I would propose something like this to start with:

That's just a .dark class in the body tag:

    <body class="dark" onload="document.querySelector('.dark-switch > input').onchange()">

...a switch at the top right:

    <label class="dark-switch"><input type="checkbox" checked onchange="document.body.classList[this.checked?'add':'remove']('dark')"/> dark</label>

...and a bit of CSS:

I also find the yellow-on-white links in your Twitter theme difficult to read.