Expose somewhere the xml feed adress in the QGIS feed admin backend

[haubourg]

Last minor glitch,
in the previous app, it was easy to find the raw xml feed as it was server at the root of the website.
I failed to find it, which is useful for debugging the real output.
@Xpirix Could you add somewhere in the QGIS feed admin screen a link to the xml feed, maybe in the menu bar entry "XML feed" . I am not sure if the feed is RSS compliant, in this case the good old RSS logo could do the trick

[Xpirix]

Hello @haubourg

Please find the proposed PR for this issue at #60.

Best regards.

[Xpirix]

The raw version is also available at: https://feed.qgis.org/?json=1