Implement the "share this page" button

[Natasha Fee]

Earlier attempts have been unsuccessful, likely due to interactions between the JS libraries used by wet-boew and by CKAN (see open-data/ckanext-canada#1191).

[Natasha Fee]

See also asc-csa/AlouetteApp#128 and asc-csa/Scisat-App#137

[Pierre Dubois]

It is possible to not use the magnific popup for the share this page widget and use instead the overlay plugin.

It will only require someone to send a PR to make that change into the wet-boew share plugin here:

• https://github.com/wet-boew/wet-boew/blob/master/src/plugins/share/share.js#L174
• https://github.com/wet-boew/wet-boew/blob/master/src/plugins/share/share.js#L216