Add note on signal prefices

SC2039.md

@@ -265,6 +265,19 @@ printf '%s' "${var}" | sed 's/some_replacement//g'
 
 No Comments / Exceptions
 
+### Prefixing signal names with `SIG`
+
+Instead of e.g.:
+```sh
+trap my_handler SIGTERM
+```
+
+use:
+```sh
+trap my_handler TERM
+# or (`trap -l` for a list of signal numbers):
+trap my_handler 15
+```
 
 ## Exception