[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/createApiMarkdown.ts

@@ -13,6 +13,7 @@ export async function createApiMarkdown() {
 		description: "Reference for the tldraw package's APIs (generated).",
 		categories: [],
 		sidebar_behavior: 'reference',
+		hero: null,
 	}
 
 	const addedCategories = new Set<string>()
@@ -55,6 +56,7 @@ export async function createApiMarkdown() {
 						id: title,
 						path: null,
 					})),
+					hero: null,
 				})
 				addedCategories.add(categoryName)
 			}