Add Sass docs (variables, mixins, and loops) to most pages (#32747)

* WIP: Mention variables, mixins, and loops in docs

* Add Sass sections to component pages

* add sass docs for forms and content

* Update buttons.md

* Remove empty mixins sections

* Massive update to utilities and some consistency changes

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

site/content/docs/5.0/utilities/text.md

@@ -82,8 +82,6 @@ Quickly change the `font-size` of text. While our heading classes (e.g., `.h1`
 
 Customize your available `font-size`s by modifying the `$font-sizes` Sass map.
 
-{{< scss-docs name="font-sizes" file="scss/_variables.scss" >}}
-
 ## Font weight and italics
 
 Quickly change the `font-weight` or `font-style` of text with these utilities. `font-style` utilities are abbreviated as `.fst-*` and `font-weight` utilities are abbreviated as `.fw-*`.
@@ -136,3 +134,21 @@ Decorate text in components with text decoration classes.
 <p class="text-decoration-line-through">This text has a line going through it.</p>
 <a href="#" class="text-decoration-none">This link has its text decoration removed</a>
 {{< /example >}}
+
+## Sass
+
+### Variables
+
+{{< scss-docs name="font-variables" file="scss/_variables.scss" >}}
+
+### Maps
+
+Font-size utilities are generated from this map, in combination with our utilities API.
+
+{{< scss-docs name="font-sizes" file="scss/_variables.scss" >}}
+
+### Utilities API
+
+Font and text utilities are declared in our utilities API in `scss/_utilities.scss`. [Learn how to use the utilities API.]({{< docsref "/utilities/api#using-the-api" >}})
+
+{{< scss-docs name="utils-text" file="scss/_utilities.scss" >}}