features: consistent punctuation

source/overview.rst

@@ -14,7 +14,7 @@ Features
 
 Subject management
     Castellum is a central place to collect references to all data related to a
-    subject, e.g. so it can be deleted on request
+    subject, e.g. so it can be deleted on request.
 
 Pseudonym service
     Contact details are stored in Castellum so all other databases can work
@@ -22,7 +22,7 @@ Pseudonym service
 
 Recruitment
     Castellum allows you to find potential subjects from an existing pool using
-    study specific filters
+    study specific filters.
 
 Appointments
     You can manage appointments for test sessions.