feat: Dune Dashboard added to the User Docs (internal)

[keriat]

Description

Add Dune dashboard embed into user docs. The zkSync stats and tvl page created on Dune.

Motivation and Context

Looks great, it is nice to have in an accessible place for one to see when looking at docs.

How Has This Been Tested?

Locally on my computer

Screen shots

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [ ] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [X] I have updated the documentation accordingly.
• [X] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

Notes

I believe premium Dune would make the dashboard slightly less cluttered at the top fyi.

[keriat]

Added as a replacement of the #206 @StanislavBreadless @stackaccount1

[github-actions[bot]]

Visit the preview URL for this PR (updated for commit 9b9fe7a):

• https://zksync-web-docs--v-refs-pull-252-merge-ejm29dv9.web.app
• https://staging-docs-zksync--v-refs-pull-252-merge-93bzzadu.web.app

_{(expires Wed, 20 Apr 2022 14:36:15 GMT)}

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