[orca-list] On Firefox Nightly, Orca is not announcing it entering inside a list

[Alex ARNAUD <aarnaud hypra fr>]

    Hello,
    
    Environment:
    - Debian 9 Stretch
    - Firefox Nightly
    - Orca master
    
    Steps to reproduce:
    1) Open this page: https://blog.documentfoundation.org/blog/2019/09/06/libreoffice-has-a-new-macro-team/
    2) Go on the line "Examples of tasks the team members have worked
    on:"
    3) Press down arrow
    
    Result:
    Orca reads the first list item
    
    Expected result:
    Orca should announce it has been entered inside a list then read the
    first list item.
    
    Best regards,
    Alex.