ReaddGitHubReleasesTab.user.js

// ==UserScript==
// @name         Readd GitHub Releases Tab
// @namespace    https://greasyfork.org/en/users/85671-jcunews
// @version      1.0.1
// @license      AGPLv3
// @author       jcunews
// @description  https://www.reddit.com/r/userscripts/comments/k39flt/request_releases_tab_for_github_userscript/
// @match        https://github.com/*/*
// @grant        none
// ==/UserScript==

(() => {
  document.querySelectorAll('a[href*="/releases"]').forEach((el, ctr, svg, nav, tab) => {
    if (ctr = el.querySelector(".Counter")) {
      svg = el.parentNode.parentNode.querySelector("svg");
      nav = document.querySelector(".UnderlineNav-body");
      (tab = document.createElement("LI")).className = "d-flex";
      tab.innerHTML = `
<a class="js-selected-navigation-item UnderlineNav-item hx_underlinenav-item no-wrap js-responsive-underlinenav-item" data-tab-item="releases-tab" data-hotkey="g r">
  ${svg ? svg.outerHTML : ""}
  <span data-content="Releases">Releases</span>
  <span title="${ctr.title}" class="Counter ">${ctr.textContent}</span>
</a>`;
      tab.firstElementChild.href = el.href;
      nav.insertBefore(tab, nav.children[1]);
    }
  });
})();