correcting contributor types for Crossref values

Signed-off-by: Neal Ensor <[email protected]>

Author: nensor

src/elinkapi/contribution.py

@@ -20,11 +20,11 @@ class Contribution(Enum):
     Researcher="Researcher"
     ResearchGroup="ResearchGroup"
     Reviewer="Reviewer"
-    ReviewerExternal="review-external"
-    ReviewAssistant="review-assistant"
+    ReviewerExternal="ReviewerExternal"
+    ReviewAssistant="ReviewAssistant"
     RightsHolder="RightsHolder"
     Sponsor="Sponsor"
-    StatsViewer="stats-reviewer"
+    StatsReviewer="StatsReviewer"
     Supervisor="Supervisor"
     Translator="Translator"
     WorkPackageLeader="WorkPackageLeader"