[NcAppSidebar] add `open` state

[ShGKme]

Currently NcAppSidebar doesn't have changeable open state. If it is rendered, it considers itself to be open. The only way to close the sidebar is basically to not render it like:

<NcAppSidebar v-if="open" />

But some apps want to keep NcAppSidebar instance even if it is not displayed.

<NcAppSidebar v-show="open" />

This breaks mobile devises, because NcAppSidebar consider itself open and enables a focus trap.

A solution could be to add open prop allowing to show/hide the sidebar keeping the component and the element in the DOM like NcAppNavigation does.

In this case, we can even render the toggle button like in Talk.

[Antreesy]

I'm afraid, same happens with NcAppNavigation too:

When it's in mobile state, focus trap is attached to toggle, and thus any open dialog would be inaccessible from keyboard (not saying that I couldn't type in TextField)

Any known PR, where this regression could come from? I could move it to a new bug issue

[ShGKme]

Hmm, with dialog it should work. Dialogs are supposed to have a focus trap, so it should stack correctly

[ShGKme]

It is different with Sidebar. The sidebar issue in Talk is that Sidebar is actually open but visually hidden.