add profiling doc

doc/topics/profile.md

@@ -0,0 +1,13 @@
+Profiling
+===================
+
+```shell
+dotenv -f .env.local -- go run -tags pprof ./cmd/bbgo run \
+    --config ./makemoney-btcusdt.yaml \
+    --cpu-profile makemoney.pprof \
+    --enable-profile-server
+```
+
+```shell
+go tool pprof http://localhost:6060/debug/pprof/heap
+```