_content/doc/fuzz: document custom settings

For golang/go#48255

Change-Id: I41f6fa5ad6eee14c265bb537fda7e4ca3ef62404
Reviewed-on: https://go-review.googlesource.com/c/website/+/372314
Reviewed-by: Bryan Mills <bcmills@google.com>
Trust: DO NOT USE <katiehockman@google.com>
Run-TryBot: DO NOT USE <katiehockman@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

_content/doc/fuzz/index.md

@@ -70,6 +70,28 @@ Below are suggestions that will help you get the most out of fuzzing.
   the end of each call, and the behavior of a fuzz target should not depend on
   global state.
 
+### Custom settings
+
+The default go command settings should work for most use cases of fuzzing. So
+typically, an execution of fuzzing on the command line should look like this:
+
+```
+$ go test -fuzz={FuzzTestName}
+```
+
+However, the `go` command does provide a few settings when running fuzzing.
+These are documented in the [`cmd/go` package docs](https://pkg.go.dev/cmd/go).
+
+To highlight a few:
+
+- `-fuzztime`: the total time or number of iterations that the fuzz target
+  will be executed before exiting, default indefinitely.
+- `-fuzzminimizetime`: the time or number of iterations that the fuzz target
+  will be executed during each minimization attempt, default 60sec. You can
+  completely disable minimization by setting `-fuzzminimizetime 0` when fuzzing.
+- `-parallel`: the number of fuzzing processes running at once, default
+  `$GOMAXPROCS`. Currently, setting -cpu during fuzzing has no effect.
+
 ## Resources
 
 - **Tutorial**: