Bug fix in the estimation of the visibility of the elements. The bug made all elements appear as hidden elements

Updated the way in which colors are evaluated so now it considers the opacity (not only applied directly to the element but also inherited) and the alpha channel when colors are defined.

Changes in the way the algorithm accesses information on each element in the DOM, so that analysis performance and time to display results are improved

Updated the way in which the colors are selected (the benefit should be improved performance)

Bug-fixing related with the document selector

Improve performance when opening the panel by ensuring only specific callbacks are executed

The main changes are:
* Visible and hidden elements are shown in the same table
* Performance improvements
* When the option for auto-refresh is deactivated, the button for executing the analysis shows a warning icon when the tool detects changes in the DOM
* Add help and release notes dialogs
* Add menu
* Layout changes

Others (list of commits on this release):
* execute only once initially
* prevent function re-declaration
* prevent update the list of documents with the DOM changes
* generate array of results data and order it before creating the results table
* simple refactor for making more easy to manipulate the results object per row
* update highlight style
* refactor how visible/hidden elements are shown
* update styles for the scroll-bars and visibility icons opacity
* update messages
* do not update table while it has the focus
* messaging on mutationObserver
* fix bug when changing to descendant documents
* fix bug with the mutationObservers
* improve resizer DOM
* improve styling
* add dialog-panel
* update help content and styles
* add spinner update only tbody for results
* add warning when DOM-mutation detected
* update layout
* add release-notes section

* Add scroll-into-view feature
* Minor changes for improving performance
* Fix bug when getting the background-color from the body
* Fix bug related with mutation observers (there were not always disconnected when closing the panel)

Added the eyedropper to pick the color directly from the document

* Fixed minor bugs
* Added information