Document Snaps data storage

[alexandratran]

Description

Add feature page on Snaps encrypted and unencrypted data storage.

Issue(s) fixed

Fixes #1262

Preview

https://docs.metamask.io/1262-snaps-storage/snaps/features/data-storage/

Checklist

Complete this checklist before merging your PR:

• [x] If this PR contains a major change to the documentation content, I have added an entry to the top of the "What's new?" page.
• [ ] The proposed changes have been reviewed and approved by a member of the documentation team.

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Preview published: 1262-snaps-storage

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Preview published: 1262-snaps-storage

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Preview published: 1262-snaps-storage

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Preview published: 1262-snaps-storage

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Preview published: 1262-snaps-storage