source: node_modules/prismjs/plugins/line-numbers/prism-line-numbers.css

pre[class*="language-"].line-numbers {
        position: relative;
        padding-left: 3.8em;
        counter-reset: linenumber;
}

pre[class*="language-"].line-numbers > code {
        position: relative;
        white-space: inherit;
}

.line-numbers .line-numbers-rows {
        position: absolute;
        pointer-events: none;
        top: 0;
        font-size: 100%;
        left: -3.8em;
        width: 3em; /* works for line-numbers below 1000 lines */
        letter-spacing: -1px;
        border-right: 1px solid #999;

        -webkit-user-select: none;
        -moz-user-select: none;
        -ms-user-select: none;
        user-select: none;

}

        .line-numbers-rows > span {
                display: block;
                counter-increment: linenumber;
        }

                .line-numbers-rows > span:before {
                        content: counter(linenumber);
                        color: #999;
                        display: block;
                        padding-right: 0.8em;
                        text-align: right;
                }