Add typeId constraint to create_adapter_manually.md

[NiklasPor]

Currently, the docs are not mentioning that there is a constraint on the custom typeId.

---

Constraint: type_registry_impl.dart

if (!internal) {
  if (typeId < 0 || typeId > 223) {
    throw HiveError('TypeId $typeId not allowed.');
  }

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[themisir]

Currently, the docs are not mentioning that there is a constraint on the custom typeId.

It mentions actually, here.