Incorrect favicon.ico location

[mtrebron]

The navigation_root_url in a multilingual site as used in
https://github.com/plone/plone.app.layout/blob/master/plone/app/layout/links/viewlets.py#L80

will not provide a canonical URL such as https://www.example.org/favicon.ico
instead, it includes the language, like https://www.example.org/de/favicon.ico

Given that we can only customize a single favicon for the site as a whole, I believe that site_url should be used instead:
https://github.com/plone/plone.app.layout/blob/master/plone/app/layout/viewlets/common.py#L64

See also #288

[yurj]

putting favicon.ico file object in /de let you customize the favicon, I think.

[mtrebron]

Sure, it lets you customize it using @@site-controlpanel but then links to a different URL for each language while displaying the same favicon.

Edit, I see what you're getting at: uploading a separate favicon image in each language root folder might indeed give you different icons depending on the navigation root. I don't know if doing so is even intended behavior, since the viewlet explicitly also tries to accommodate RSS readers and apps...