AppNavigation: fix style for CSS class "active"

[korelstar]

Since #486, #app-navigation has CSS class vue and Nextcloud server has the following style:

#app-navigation:not(.vue) > ul > li.active, #app-navigation:not(.vue) > ul > li a:hover, #app-navigation:not(.vue) > ul > li a:focus, #app-navigation:not(.vue) > ul > li a:active, #app-navigation:not(.vue) > ul > li a.selected, #app-navigation:not(.vue) > ul > li a.active, #app-navigation:not(.vue) > ul > li.active > a, #app-navigation:not(.vue) > ul > li a:hover > a, #app-navigation:not(.vue) > ul > li a:focus > a, #app-navigation:not(.vue) > ul > li a:active > a, #app-navigation:not(.vue) > ul > li a.selected > a, #app-navigation:not(.vue) > ul > li a.active > a {
	opacity: 1;
	box-shadow: inset 4px 0 var(--color-primary);
}

This means, that the active style from server is not applied anymore to AppNavigationItem. However, the component doesn't include it's own style for active CSS class. This is fixed with this PR.

[skjnldsv]

Ah, we have an ongoing discussion about this in #425 :)
Which will also be applied to the navigation, so we'll wait for it to be integrated I think! @ma12-co ?

[korelstar]

I'm aware of that. But it's unclear when this will be implemented. Currently, there is no way to identify the active item at all. Therefore, I think this intermediate quick-fix is helpful. Otherwise, testing an app using master is very annoying.

[skjnldsv]

@korelstar ahah, sorry :)
Let's merge this then sure!

[skjnldsv]

/backport to stable0-12

[backportbot-nextcloud]

The backport to stable0-12 failed. Please do this backport manually.

[skjnldsv]

Ah no, too different, let's keep on 13.0.x