[docs] design shuffle (#2951)

This PR incorporates design tweaks from #2922 without the home page or
content changes.

These are:
- Replacing all `hello@tldraw.com` with `sales@tldraw.com`
- Fix mailto links.
- Showing the first item in a section on direct routes to the section
- Splitting the article page for human-written content from article page
for generated content
- Splitting the layout for the landing page from the rest of the site
(temporarily identical to the regular content)
- Removing headings from left sidebar
- Restoring headings in right sidebar for human-written pages with > 1
heading link
- Styling block quote
- Adjusting section link appearance / layout in header / menu
- Changing the order of search results to preference docs over examples
- Updating copy on events
- Removing copy on user interface menus
- Adding hero as prop to all articles
- Updated icon
- Fixing a few broken links
- Replaces the sandpack code blocks with hljs code blocks, except in
examples.

### Change Type

- [x] `documentation` — Changes to the documentation only[^2]

apps/docs/scripts/functions/generateSection.ts

@@ -166,6 +166,7 @@ export function generateSection(section: InputSection, articles: Articles, index
 			groups: [],
 			path: `/${section.id}/ucg`,
 			content: null,
+			hero: null,
 		},
 	]
 
@@ -188,6 +189,7 @@ export function generateSection(section: InputSection, articles: Articles, index
 				index: i + 1,
 				path: `/${section.id}/${inputCategory.id}`,
 				content: null,
+				hero: null,
 				groups: inputCategory.groups.map(({ id }, i) => ({
 					id,
 					title: id,
@@ -210,6 +212,7 @@ export function generateSection(section: InputSection, articles: Articles, index
 		index,
 		categories,
 		content: '',
+		hero: section.hero ?? null,
 		path: `/${section.id}`,
 	}
 }