fix: Skip editor container and file upload input during keyboard navigation

[juliusknorr]

Fix https://github.com/nextcloud/andy/issues/8

The hidden input[type=file] is used by the image menu action to trigger a file upload but does not need to be interacted with. I'm not entirely sure why the #editor-container is considered a focussable dom element, but having the tabindex disabled there fixes the tab navigation to be logical.

[juliusknorr]

/backport to stable28

[ShGKme]

Note, this input has at the same time:

• aria-hidden="true" = element should not be visible to assistive technologies like a decorative element
• class="hidden-visually" = element should be visible via assistive technologies and only hidden visually for a general user

It doesn't make sense to use them simultaneously (except some very specific cases).

If it is a completely hidden element used only programmatically, it can be hide by display: none (v-show="false"). This also makes it not focusable and hidden for assistive technologies.

Examples of correct using class="hidden-visually":

• Hiding a heading, label elements
• Hiding input checkbox/radio, when whey are still directly accessible via keyboard or mouse but invisible because of using a custom icon

[juliusknorr]

Thanks for the insight, wasn't aware of that difference.

PR in #5230