JSFiddle - React, Tailwind, and code Playground

HTML

<ol class="first_lvl">
    <li><span>Пункт</span>
        <ol class="second_lvl">
            <li>Подпункт</li>
            <li>Подпункт</li>
        </ol>
    </li>
    <li><span>Пункт</span>
        <ol class="second_lvl">
            <li>Подпункт</li>
            <li>Подпункт</li>
        </ol>
    </li>
</ol>

CSS

ol {
     list-style: none;   
}

.first_lvl {
    counter-reset: firstLvl;
}

.first_lvl > li span:before {
    content: counter(firstLvl) '. '; 
    counter-increment: firstLvl;  
}

.second_lvl {
    counter-reset: secondLvl;   
}

.second_lvl > li:before {
    content: counter(firstLvl) '.' counter(secondLvl) '. ';
    counter-increment: secondLvl;   
}