more debugging tips

README.md

@@ -14,12 +14,13 @@ Test runs infinitely? Build the test program executable:
 
 And then run it, capturing the stack trace:
 
+```
 gdb -batch \
     -ex "python import threading; threading.Timer(1.0, lambda: gdb.post_event(lambda: gdb.execute('interrupt'))).start()" \
     -ex run \
     -ex "bt full" \
     -ex quit \
     zig-out/bin/test
-
+```
 
 You are welcome to replace `-ex "bt full"` with anything other of interest.