Add links to official docs site.

For more details: https://ropensci.org/technotes/2019/06/07/ropensci-docs/

Author: rOpenSci Bot

DESCRIPTION

@@ -19,7 +19,7 @@ Description: Contains functions for developing phylogenetic trees as
     manipulation and import/export via Newick parenthetic text.
 License: GPL-3
 LazyData: TRUE
-URL: http://github.com/ropensci/phylogram
+URL: https://docs.ropensci.org/phylogram, http://github.com/ropensci/phylogram
 BugReports: http://github.com/ropensci/phylogram/issues
 Encoding: UTF-8
 Imports: