Add documentation for GPS waypoint following introduces in pull/2111 at navigation2

[jediofgever]

Add documentation related to ros-navigation/navigation2#2111 to navigation.ros.org

SteveMacenski ;

• We also need any new parameters or actions exposed by the waypoint follower added to the navigation.ros.org website configuration docs.
• Also adding a node in the migration guide that WP follower now does GPS in the Foxy migration guide.
• The WP follower configuration page should also add a paragraph on top with the basic package description mentioning GPS waypoint following now.

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jediofgever;

• following navsat_transform_node params needs to be set true, which will be covered in navigation.ros.org PR;
  broadcast_utm_transform: true
  broadcast_utm_transform_as_parent_frame: true