Utilizing a code block in Markdown format results in its conversion to HTML code, encapsulated within <pre><code> markup. By default, there is no line numbering; it’s a straightforward code block display. To incorporate line numbering and apply some CSS styling through SCSS, I employed vanilla JavaScript code:

(function() {
  var pre = document.getElementsByTagName('pre'),
      pl = pre.length;
  for (var i = 0; i < pl; i++) {
    pre[i].innerHTML = '<span class="line-number"></span>' + pre[i].innerHTML + '<span class="cl"></span>';
    var num = pre[i].innerHTML.split(/\n/).length;
    for (var j = 0; j < (num - 1); j++) {
      var line_num = pre[i].getElementsByTagName('span')[0];
      line_num.innerHTML += '<span>' + (j + 1) + '</span>';
    }
  }
})();

My SCSS code:

code,
pre {
    font-family: $font-precode;
    font-variant-ligatures: none;
    font-feature-settings: "liga" 0;
}

code {
    background: var(--code-bg);
    color: var(--code-color);
}

pre {
    width: 100%;
    margin: 0 0 1rem 0;
    line-height: 1.4;
    white-space: pre;
    overflow: auto;
    padding: 0.5rem 2rem 0.5rem 0.5rem;
    font-size: 0.9rem;
    code {
        padding: 0;
    }
    .line-number {
        float: left;
        margin: 0 1em 0 -1em;
        user-select: none; /* Standard */
        text-align: right;
        span {
            display: block;
            padding: 0 0.5em 0 1em;
        }
    }
    .cl {
        display: block;
        clear: both;
    }
}