Introducing limits

[hackerwins]

What would you like to be added:

Yorkie has no limits yet. It would be nice to add limits as below.

Key	Name	Description
max-document-bytes	Maximum document size	Yorkie saves snapshots for quick document rebuilds. If the snapshot of the document gets bigger, it may exceed the limit of DB. The size of one field must not exceed the maximum size of a document.

• BSON Document Size in MongoDB
• https://firebase.google.com/docs/firestore/quotas?hl=ko

Why is this needed:

The service can be stably provided with restrictions that match the characteristics.

[hackerwins]

related with #267

[kokodak]

I'm interested in working on this issue, but I think we need to have a policy discussion about saving snapshots.

There was an assignee on issue #267, and I'm wondering if there is any background on what they were working on before.

If there is any background or planned direction for this issue, could you share some context?