Improve accessibility (part 6) (#4435)

* fix(status_action_bar): Use aria-pressed for reblog and favourite button

* fix(column_back_button): Keyboard accessible

* fix(status_content): Make focusable and accessible

* fix(dropdown_menu): Use aria-expanded instead of aria-pressed

* fix(emoji_picker_dropdown): Use aria-expanded instead of aria-hidden

* feat(icon_button): Add aria-expanded

* fix(privacy_dropdown): Use aria-expanded instead of aria-hidden