Added rule for trailing comma in enums.

docs/development/CodingStyle.md

@@ -126,6 +126,19 @@ and no space around the '.' and "->" structure member operators.
 '*' and '&', when used for pointer and reference, shall have no space between it and the following variable name.
 
 # typedef
+enums that do not have a count or some other form of terminator element shall have a comma after their last element:
+
+```
+typedef enum {
+    MSP_RESULT_ACK = 1,
+    MSP_RESULT_ERROR = -1,
+    MSP_RESULT_NO_REPLY = 0,
+    MSP_RESULT_CMD_UNKNOWN = -2,
+} mspResult_e;
+```
+
+This ensures that, if more elements are added at a later stage, only the additional lines show up in the review, making it easier to review.
+
 enums with a count should have that count declared as the last item in the enumeration list,
 so that it is automatically maintained, e.g.:
 ```