Add note to docs that private fields of structs cannot be fuzzed using this package about gofuzz

[lavalamp]

Yes, you're correct, and I agree a note in the README seems useful.

[ericcornelissen]

I'm not sure where in the README you would want to add this, but I think having a note somewhere stating something as simple as:

"gofuzz cannot set the value of private fields."

Would suffice.

Maybe after the first example with a struct like so:

---

...
Customize the chance of getting a nil pointer:

f := fuzz.New().NilChance(.5)
var fancyStruct struct {
  A, B, C, D *string
}
f.Fuzz(&fancyStruct) // About half the pointers should be set.

ℹ️ Note: gofuzz cannot set the value of private fields.

You can even customize the randomization completely if needed:
...

---

Or just at the end of the document, so that it's easy in the future to add more notes like this one:

---

...
Happy testing!

Caveats

• gofuzz cannot set the value of private fields.

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