fix(NcRichContenteditable): unify styles and add contrast border on keyboard navigation

[ShGKme]

☑️ Resolves

• Fix [BITV] 9.2.4.7/3.1 - In the "Details" section under the "Activity" tab, it is possible to open a dropdown list when entering "@", ":" or "/" into the textbox (2) nextcloud/server#41879

Adds a contrast outline border for keyboard navigation only.

Also, unifies styles in different autocompletes with NcActions and NcSelect components.

Previously, there were no "general" styles for the tribute container and items. Different autocompletes had a bit different styles on always individual classes. Now:

• There are common classes and structure is always:

  div.tribute-container (+ additional custom .tribute-container-NAME)
    ul
      li.tribute-container__item (+ .highlight + .tribute-container-NAME__item)
        div.tribute-item
          <custom content>
  

• An autocomplete item now:
  • Always has padding
  • Always has border radius
  • Always has hover background color same as NcSelect or NcActions

🖼️ Screenshots

🏚️ Before	🏡 After

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable