Add horizontal padding for mobile

[phultquist]

I was browsing wasmbyexample.dev on my phone when I realized the text inside a container class was a little bit hard to read because the lack of horizontal padding. This PR adds that ✅

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[torch2424]

@phultquist Ah! This looks great! Thanks for catching that, I tested the deploy preview and yeah it looks much better on mobile now haha! Thank you very much for the PR! Approving and merging! 😄 🙏🏾