Update Create Bookmark from Current Tab in Chrome.applescript

Added ability to populate Spillo's Description field with the currently selected text in the Chrome tab. (It is optional behavior: if no selection, Description is not populated.) 

Note: Due to Chrome's refusal to execute javascript via Applescript, we must rely on the clipboard, so the current clipboard contents are replaced with selected text when this script runs. Code could be added to save the clipboard's current contents, do the Spillo automation and then place the original contents back on the clipboard at the script's end.