feat: add navigation

[itsacoyote]

What 💻

• Adds navigation for Build, ZK Stack and External Node
• Moves /content directory around to match site navigation structure

Why ✋

• Need to add in the other sections of the docs website

[github-actions]

Visit the preview URL for this PR (updated for commit dcc9b68):

https://zksync-docs-staging-5eb09--pr19-add-navigation-7tn6tm1n.web.app

_{(expires Thu, 25 Apr 2024 20:42:40 GMT)}

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_{Sign: bfaafba5fa82d4f63473aaa76a21fabf1fbb3a11}

[dutterbutter]

@itsacoyote the search input box is no longer present, is that intentional?

[dutterbutter]

Also I think it would be a good idea to have ZK Stack have its own "landing page". Thoughts?

[itsacoyote]

Also I think it would be a good idea to have ZK Stack have its own "landing page". Thoughts?

Like similar to the current landing page it has on the docs site?

[itsacoyote]

@itsacoyote the search input box is no longer present, is that intentional?

Forgot to put it back in somewhere else.

[dutterbutter]

Also I think it would be a good idea to have ZK Stack have its own "landing page". Thoughts?

Like similar to the current landing page it has on the docs site?

Probably more dressed up. We can discuss this offline but given its own framework we may be able to give the landing page some excitement. Similar to https://substrate.io/ although less complicated.