Reorder translations and add missing prefixes

- files should be prefixed with code_ocean/
- the markdown editor is part of the application (helper)

config/locales/en/study_group_membership.yml

@@ -0,0 +1,9 @@
+---
+en:
+  activerecord:
+    attributes:
+      study_group_membership:
+        role: Role
+        role_type:
+          learner: Learner
+          teacher: Teacher