Some already have them (T330432: Update existing foreign-resources.yaml files to add extra fields for some known ones)...
While many don't have 3rd party libraries, many do, so should be added, along with a maintenance script to run the ForeignResourceManager...
T330427: Add a way for skins and extensions to feed into "Installed client-side libraries" on Special:Version has been done, exposing this data.
T330508: Expand running of ForeignResourceStructureTest against skins and extensions that have foreign-resources.yaml files is still to be done, wiring it into our CI...