Fit the app-navigation to css guidelines [$20 awarded]

[skjnldsv]

Refs: https://docs.nextcloud.com/server/12/developer_manual/app/css.html

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The $20 bounty on this issue has been claimed at Bountysource.

[skjnldsv]

Blocked by #528

[ChristophWurst]

@nextcloud/mail FYI if we don't come up with a solution for this issue (the app looks totally crappy at the moment) I will tag this app as incompatible with NC13 and also upload a patch release to the app store to make sure people don't install a non-compatible app.

Unfortunately, this shouldn't even have happened but I've made the mistake (again, happened with the TOTP app too already) of uploading a release to the app store that was compatible with the upcoming Nextcloud server. As things are likely to break (we're not as stable as I wish we were) we should never ever release any app as compatible with anything newer than the latest stable release of the Nextcloud server.

[skjnldsv]

Can we close this then? :)

[ChristophWurst]

Sure. @skjnldsv don't forget to claim your bounty at https://www.bountysource.com/issues/49232072-fit-the-app-navigation-to-css-guidelines 😉