style(web): Responsive styles for home page

[yuedanlabs]

The laf.dev home page doesn't support responsive styles currently.

This PR add some styles to support it, and the result display as below.

• screen width 640px - 768px, the left is currently laf.dev page, and the right is the result.

• screen width 768px - 1024px, the left is currently laf.dev page, and the right is the result.

• screen above 1024px is the same as laf.dev, there is no changes.

And more,

there is still some other styles should to fix or improve, if this pr is accept, I will do more about this inside other pages(but a ).

[cla-assistant]

All committers have signed the CLA.

[cla-assistant]

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