Create a custom link browser

use TYPO3\CMS\Backend\Controller\AbstractLinkBrowserController;
use TYPO3\CMS\Core\Page\PageRenderer;
use TYPO3\CMS\Core\View\ViewInterface;

class GitHubLinkHandler implements LinkHandlerInterface
{
    protected array $linkAttributes = ['target', 'title', 'class', 'params', 'rel'];

    protected array $linkParts = [];

    protected ViewInterface $view;

    protected array $configuration;

    public function __construct(
        // The page renderer is needed to register the JavaScript
        private readonly PageRenderer $pageRenderer,
    ) {}

    public function initialize(AbstractLinkBrowserController $linkBrowser, $identifier, array $configuration)
    {
        $this->configuration = $configuration;
    }

    public function setView(ViewInterface $view): void
    {
        $this->view = $view;
    }
}

services:
  _defaults:
    autowire: true
    autoconfigure: true
    public: false

  T3docs\Examples\LinkHandler\GitHubLinkHandler:
    public: true
    # The link handler keeps a state and can therefore be no singleton
    shared: false

use Psr\Http\Message\ServerRequestInterface;

class GitHubLinkHandler implements LinkHandlerInterface
{
    public function render(ServerRequestInterface $request): string
    {
        $this->pageRenderer->loadJavaScriptModule('@t3docs/examples/github_link_handler.js');
        $this->view->assign('project', $this->configuration['project']);
        $this->view->assign('action', $this->configuration['action']);
        $this->view->assign('linkParts', $this->linkParts);
        $this->view->assign('issue', $this->linkParts['issue'] ?? '');

        return $this->view->render('LinkBrowser/GitHub');
    }
}

/*
 * This file is part of the TYPO3 CMS project.
 *
 * It is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License, either version 2
 * of the License, or any later version.
 *
 * For the full copyright and license information, please read the
 * LICENSE.txt file that was distributed with this source code.
 *
 * The TYPO3 project - inspiring people to share!
 */

import LinkBrowser
	from "@typo3/backend/link-browser.js";

/**
 * Module: @t3docs/examples/github_link_handler.js
 * Github issue link interaction
 */

class GitHubLinkHandler {
	constructor() {
		var form_el = document.getElementById("lgithubform");
		form_el.addEventListener("submit", function(event) {
			event.preventDefault();
			var value = document.getElementById('lgithub').value;
			if (value === 't3://github?issue=') {
				return;
			}
			if (value.indexOf('t3://github?issue=') === 0) {
				value = value.substring(18);
			}
			LinkBrowser.finalizeFunction('t3://github?issue=' + value);
		});
	}
}

export default new GitHubLinkHandler();

<?php

return [
    'dependencies' => ['backend'],
    'imports' => [
        '@t3docs/examples/' => 'EXT:examples/Resources/Public/JavaScript/',
    ],
];

class GitHubLinkHandler implements LinkHandlerInterface
{
    public function canHandleLink(array $linkParts): bool
    {
        if ($linkParts['type'] !== 'github') {
            return false;
        }
        $this->linkParts = $linkParts['url'] ?? [];
        return true;
    }
}