docs: port to VitePress

Things that happen in this shameless squash:
- Removed 404 page
  - It doesn't work in VitePress and making it work in VitePress needs
    some invasive hack in the theme that I'm not willing to do
  - The default is more than enough, though
- Moved consoleVersionSelect include to another directory
  - This avoids being uploaded to Crowdin for translation
- Inline all SafeB9SInstaller includes
  - Not only do parameterized includes not work, but if/else statements
    don't work at all
- The sysupdate include parameter hasn't been used since MSET9, so it
  actually works just fine without any parameters. Hooray(?)
- Move mset9-chorus to an include, that logic doesn't work in VitePress
- Removed Get Started button from homepage, it breaks translations
- Tables in get-started are now shown by default; it seems VitePress really does
  not want us to use inline script. So we cannot enable it upon
  realizing that the browser is JS capable
- Include parameters are now in frontmatter to allow translation
- Hacked in a bunch of CSS values kanged from the old theme to make it
  look not stupid
- Drop headers down one level to make table of contents work

docs/index.md

@@ -1,23 +1,24 @@
 ---
-layout: splash
-title: "3DS Hacks Guide" #
-header:
-  overlay_color: "#5e616c" #
-  overlay_image: /images/home-page-feature.jpg
-  overlay_filter: 0.5
-  cta_label: "Get Started"
-  cta_url: "key-information"
-  caption:
-excerpt: "A complete guide to 3DS (and 2DS) custom firmware, <br /> from stock to boot9strap.<br />"
+layout: home
+title: "3DS Hacks Guide"
+hero:
+  text: "3DS Hacks Guide"
+  tagline: "A complete guide to 3DS (and 2DS) custom firmware, from stock to boot9strap."
+  image:
+    src: /images/home-page-feature.jpg
 ---
 
+::: info
+
 Thoroughly read all of the introductory pages (including this one!) before proceeding.
-{: .notice--info}
 
-{% capture update-notice %}
-{% include_relative include/3ds-online.txt %}
-{% endcapture %}
-<div class="notice--danger">{{ update-notice | markdownify }}</div>
+:::
+
+::: danger
+
+<!--@include: ./_include/3ds-online.md -->
+
+:::
 
 ## What is custom firmware?
 
@@ -43,5 +44,8 @@ This guide will:
 
 ___
 
-### Continue to [Key Information](key-information)
-{: .notice--primary}
+::: tip
+
+Continue to [Key Information](key-information)
+
+:::