fix: move particles on landing page behind content on page

[MexicanAce]

Description

Move the particles animation (on the landing page) to behind the content displayed

Linked Issues

Additional context

[github-actions[bot]]

Visit the preview URL for this PR (updated for commit 83acca9):

https://zksync-docs-staging-5eb09--pr133-nmv-fix-particle-z-i-87z6ranl.web.app

_{(expires Sun, 23 Jun 2024 09:35:34 GMT)}

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[github-actions[bot]]

:tada: This PR is included in version 1.2.1 :tada:

The release is available on GitHub release

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