Resolve "Tooltips break some links"

Closes #1 (closed)

extension/common.js

@@ -22,11 +22,33 @@
 // Shared code
 
 
+/**
+ * Regexp that matches safe links. The original URL must be collected
+ * in match group 1.
+ */
 const safelinksRegexp = new RegExp(
     'https?://[^.]+[.]safelinks[.]protection[.]outlook[.]com/[?]url=([^&]+)&.*',
     'gi'
 );
 
+
+/**
+ * The ID for the popup element that is added to the HTML document.
+ */
+const safelinksPopupId = 'safelinks-cleaner-thunderbird-popup';
+
+
+/**
+ * The class that is added to the popup when visible.
+ */
+const safelinksPopupVisibleClass = 'safelinks-cleaner-thunderbird-popup-visible';
+
+
+/**
+ * Return the original URL for a safe link.
+ * @param {string} link - The safe link.
+ * @returns {string} The original link or the safe link if there was an error.
+ */
 function untangleLink(link) {
     return link.replaceAll(
 	safelinksRegexp, (match, url) => {
@@ -40,10 +62,22 @@ function untangleLink(link) {
 	});
 }
 
+
+/**
+ * Check if a link is a safe link.
+ * @param {string} link - The URL to check.
+ * @returns {boolean} Returns true if the link is a safe link.
+ */
 function isTangledLink(link) {
     return link.match(safelinksRegexp);
 }
 
+
+/**
+ * Return the text nodes under a DOM element.
+ * @param {Element} elem - The element to return text nodes for.
+ * @returns {Element[]} The text elements under elem.
+ */
 function getTextNodes(elem) {
     var result = [];
     if (elem) {