docs: Add warnings to doc requirements doc
Document how other admonitions such as warnings and hints should be
handled.
Fixes
* [Introduction](#introduction)
* [General requirements](#general-requirements)
* [Notes](#notes)
+* [Warnings and other admonitions](#warnings-and-other-admonitions)
* [Files and command names](#files-and-command-names)
* [Code blocks](#code-blocks)
* [Images](#images)
@@ -35,6 +36,24 @@ If there are multiple notes, bullets should be used:
>
> - I am important point *n*.
+# Warnings and other admonitions
+
+Use the same approach as for [notes](#notes). For example:
+
+> **Warning:** Running this command assumes you understand the risks of doing so.
+
+Other examples:
+
+> **Warnings:**
+>
+> - Do not unplug your computer!
+> - Always read the label.
+> - Do not pass go. Do not collect $200.
+
+> **Tip:** Read the manual page for further information on available options.
+
+> **Hint:** Look behind you!
+
# Files and command names
All filenames and command names should be rendered in a fixed-format font
