Foxy Gestures user script.

openSelectedLinks.js

const hrefs = window.getSelection().getRangeAt(0).cloneContents().querySelectorAll('a');
const urls = Array.from(hrefs)
    .map(link => link.href)
    .filter(link => link.match(/^(http|file)/i));
executeInBackground(urls => {
    getActiveTab(tab => {
        for (const [i, url] of urls.entries()) {
            browser.tabs.create({
                url: url,
                index: tab.index + 1 + i,
                active: false
            });
        }
    });
}, [urls]);