Features
            Shows a list of headings with information about their level and if they break the hierarchical structure
            
            If there are elements that use role attribute with value heading, they are also listed. Their level is based on the value of <em>aria-level</em> attribute (if not defined, its default is 2).
            
            List of sections with header information and warnings for errors in the structure
            Gets the information from the main document and also from the documents inside iframes (includes a document selector that is active when there are multiple documents)
            
            By clicking on the headers, the document scrolls to the position of the header/section and highlights it
            
            Detects changes in the DOM and when they finish it updates the trees
            Dark theme (optional)
            HTML 5 Outline test is optional
            Optionally it shows hidden headers and sections (hidden for assistive technologies). When they are shown, an icon is added to the items in the tree to identify which ones were detected as visible or hidden by the extension
            
            If the header (or section) is an anchor, the link in the results has the href pointing to it (useful for being copied directly from the tree with the option in the contextual menu of the browser)
            
            If header/section content uses aria-label, its value can be shown (optional property configurable in the settings section)
            
            Version for multiple browsers. It uses the "browserExtensions API" so it is compatible with Chrome, Firefox, Microsoft Edge,...