Add security certificate

[tucotuco]

From Bob Mesibov,

I haven't used the Georeferencing Calculator myself, but I note that the online version isn't going to be opened by browsers that look for a security certificate (url still http, not https), the layout code fails in some browsers (e.g. my Firefox 81; see attached screenshot) and is non-conformant (e.g. the title and link elements are outside ).