link popup improvements (code included)

[liedekef]

I added this listener to improve the link popup window a bit (adding mailto: and https:// if needed, so people don't need to know this):

        editor.events.on('afterOpenPopup.link', (popup) => {
            const urlField = popup.container.querySelector('input[data-ref="url_input"]');
            if (!urlField) return;

            const urlval = urlField.value.trim();
            if (!urlval) {
                const contentval = popup.container.querySelector('input[data-ref="content_input"]').value.trim();
                if (/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(contentval)) {
                    urlField.value = 'mailto:' + contentval;
                } else if (/^(https?:\/\/)/i.test(contentval)) {
                    urlField.value = contentval;
                } else {
                    urlField.value = 'https://' + contentval;
                }
            }
        });