Enforce heading order

See https://dequeuniversity.com/rules/axe/4.8/heading-order

Author: meator

src/package-update-tutorial.md

@@ -5,7 +5,8 @@
 This tutorial will guide you through updating an already existing package using
 `xbps-src`.
 
-### Prerequisites
+**Prerequisites**
+
 - basic knowledge of Git
 - basic knowledge of GitHub for contributing (have an account, know how to make
   a pull request)

src/packaging/index.md

@@ -10,7 +10,8 @@ This tutorial will guide you through packaging using `xbps-src` for inclusion
 in [void-packages](https://github.com/void-linux/void-packages) repository or
 for personal use.
 
-### Prerequisites
+**Prerequisites**
+
 - use Void Linux (this is not a hard requirement, there are ways to build XBPS
   packages from foreign distros, but this is outside the scope of this tutorial)
 - basic knowledge of Git
@@ -24,7 +25,8 @@ for personal use.
   (they are used in [packaging j4-dmenu-desktop](/packaging/j4-dmenu-desktop.md)
   section of this tutorial, but shouldn't be necessary in more normal use)
 
-### Non-prerequisites
+**Non-prerequisites**
+
 This tutorial assumes no prior knowledge of packaging systems.
 
 ---

src/pr-testing-tutorial.md

@@ -5,7 +5,8 @@
 This tutorial will guide you through testing changes made in an open pull
 request in [`void-packages`](https://github.com/void-linux/void-packages).
 
-### Prerequisites
+**Prerequisites**
+
 - basic knowledge of Git
 - basics of CLI