Bundle CSS with Hugo's Sass feature (#705)

* migrate bootstrap and flags to bundle

* migrated main.css

* migrate navbar.css and plyr

* migrated mulish font and darkreader

* migrated static/css/sections stylesheets

* migrated list page and sidebar styles

* migrated search.html ( nothing to add )

* migration single page styles

* remove duplicated style tags

* migrate notes.  Deleted unused css in static

* migrate 404 css to bundle

* migrate katex styles

* migrate embedpdf styles

* migrated katex css

---------

Co-authored-by: Aaron Qian <aaron@yeet.io>

layouts/notes/single.html

@@ -1,12 +1,3 @@
-{{ define "header" }}
-  <link
-    rel="stylesheet"
-    href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.18.1/styles/atom-one-dark.min.css"
-  />
-  <link rel="stylesheet" href="{{ "/css/layouts/notes.css" | relURL}}">
-  <link rel="stylesheet" href="{{ "/css/navigators/sidebar.css" | relURL}}">
-{{ end }}
-
 {{ define "navbar" }}
     {{ partial "navigators/navbar-2.html" . }}
 {{ end }}
@@ -45,9 +36,3 @@
   </div>
 </section>
 {{ end }}
-
-{{ define "scripts" }}
-  {{ if site.Params.features.math.enable }}
-      {{ partial "math.html" . }}
-  {{ end }}
-{{ end }}