Get links base on base URL
get_links(base_url)A base URL (the base part of the web address)
The function returns a dataframe of three columns ("href", "link_text", and "link"). If the function runs into an error getting the links based on the base URL, the value of the href column should be NA. The link_text will inform the error case. This should be either "This website is broken.", "The website is flat (no tree structure)." or "The website does not have about page."