feat: add docs for async transform

[fxwss]

🔗 Linked issue

Issue #72 - async transform

❓ Type of change

• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Await all transform functions on schema.validate and schema.tryValidate calls;
Add a option to ValidationOptions called shouldAwaitTransformers, an boolean that indicates when the transformers should be awaited. Defaults to undefined.

Resolves #72

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.