revuo-weekly/_includes/header-custom.html

<style>
.switch {
  position: relative;
  display: inline-block;
  width: 60px;
  height: 34px;
  margin-top: 0px;
}

.switch input { 
  opacity: 0;
  width: 0;
  height: 0;
}

.slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: #ccc;
  -webkit-transition: .4s;
  transition: .4s;
}

.slider:before {
  position: absolute;
  content: "";
  height: 26px;
  width: 26px;
  left: 4px;
  bottom: 4px;
  background-color: white;
  -webkit-transition: .4s;
  transition: .4s;
}

input:checked + .slider {
  background-color: #2196F3;
}

input:focus + .slider {
  box-shadow: 0 0 1px #2196F3;
}

input:checked + .slider:before {
  -webkit-transform: translateX(26px);
  -ms-transform: translateX(26px);
  transform: translateX(26px);
}

/* Rounded sliders */
.slider.round {
  border-radius: 34px;
}

.slider.round:before {
  border-radius: 50%;
}

table {
  margin-top: 34px;
}

td {
  height: 50px;
  vertical-align: middle;
}
</style>



<!--<label class="switch">-->
  <!--<input type="checkbox" checked>-->
  <!--<span class="slider round"></span>-->
<!--</label>-->
<header id="header">

	<!-- Your custom header here -->
	<div>
        <a href="{{ site.baseurl }}">
		  <img src="{{ "/img/revuo-monero-logo.png" | prepend: site.baseurl | replace: '//', '/' }}" alt="Revuo Monero Logo">
	    </a>
    </div>
    <div class="revuo-classes">
        <a href="{{ site.baseurl }}" class="wk">Weekly</a>
        <a href="/periodicals/" class="pd">Periodical</a>
    </div>

    <!--Add dark mode here-->
	<div>
    <table align="center">
	<tr>
	    <td>
	    <img src="{{ "/img/dark-theme-icon2.png" | prepend: site.baseurl | replace: '//', '/' }}" height="50px" width="50px" alt="Dark Theme">
	    </td>

	    <td>
<label class="switch">
  <input type="checkbox">
  <span class="slider round"></span>
</label>

	    </td>
	</tr>
    </table>
	</div>

    <!--Finish dark mode-->
	
</header>