feat: add SEO support

[VanishMax]

• Added better SEO support
• Added images for favicon and logo
• Removed the empty footer, added Discord link, fixed the link to GitHub tree
• Ensured consistency across the pages to have H1 tag
• Created empty pages, so the links don't point to nothing

[github-actions]

Visit the preview URL for this PR (updated for commit ad107e3):

https://penumbra-guide--pr7-feat-seo-xs3p9ro4.web.app

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[hdevalence]

Ah, I was cutting these out and replacing them with a title: attribute since the title is already displayed at the top of the article and it looked weird to duplicate (even if the top display is in smaller text)

[VanishMax]

Agree on weirdness. The top title is actually a breadcrumbs link. It can't be used as a title since it is small in size and, if the page is nested, it renders as "page1 -> page2".

I found a way to remove the breadcrumbs from the first-level pages (e.g. /dex but not /web/prax), and it looks better now:

And here are nested pages:

[hdevalence]

OK Cool, good fix