[css-lists] The 'list item' definition needs to include multi-keyword 'display' values

The list item definition needs to be updated to account for the new multi-keyword display values. Any valid display value that includes the list-item keyword is now a list item.

Also, the Introduction section says "the list-item display type that generates markers", however the list-item word there is linkified to the list-item counter definition, which I assume is not what you intended. And you need to generalize that statement to include all possible display types too.

Ditto for "The defining feature of the list item display type is its marker" in Markers (which is also missing a dash between "list" and "item", btw)

(FYI, I'm implementing the new multi-keyword display values and on top of that inline list-item values in Gecko.)

Read the linked CSS Lists definition, Introduction section, and Markers section, comparing their wording with the linked CSS Display multi-keyword values. Done means updating the list-item definition and related statements to cover any display value containing list-item, while correcting the incorrect counter link and missing hyphen.