chore: add main pkg URL

Author: salim-b

DESCRIPTION

@@ -7,7 +7,7 @@ Authors@R:
 Description: Provides unofficial helper functions around the plotly
     package, the R API for the JavaScript graphing library plotly.js.
 License: AGPL (>= 3)
-URL: https://gitlab.com/rpkg.dev/plotlee
+URL: https://plotlee.rpkg.dev, https://gitlab.com/rpkg.dev/plotlee
 BugReports: https://gitlab.com/rpkg.dev/plotlee/-/issues
 Depends: 
     R (>= 4.4)