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/site-navigation.md

@@ -1,19 +1,18 @@
----
-title: "Site Navigation" #
-sitemap: false
----
+# Site Navigation
+
+::: tip
 
-{% capture notice-1 %}
 **Popular**
 
 + [Finalizing Setup](finalizing-setup)
 + [Installing boot9strap (Soundhax)](installing-boot9strap-(soundhax))
 + [Installing boot9strap (MSET9)](installing-boot9strap-(mset9))
 
-{% endcapture %}
-<div class="notice--info">{{ notice-1 | markdownify }}</div>
+:::
+
+
+::: info
 
-{% capture notice-2 %}
 **All**
 
 + [A9LH to B9S](a9lh-to-b9s)
@@ -56,5 +55,5 @@ sitemap: false
 + [Troubleshooting](troubleshooting)
 + [Uninstall CFW](uninstall-cfw)
 + [Updating B9S](updating-b9s)
-{% endcapture %}
-<div class="notice--primary">{{ notice-2 | markdownify }}</div>
+
+:::