....turns out there *is* a GH alert markdown-it plugin!

Thanks, markdown-it-github-alerts :D
A bit of CSS ~~hackery~~ magic and we're away!

.docs/css/theme.css

@@ -442,26 +442,50 @@ footer {
 	border: 0.2em solid var(--cat-colour);
 }
 
-.note, .tip, .important, .warning, .caution {
+.note, .tip, .important, .warning, .caution
+.markdown-alert-note,
+.markdown-alert-tip,
+.markdown-alert-important,
+.markdown-alert-warning,
+.markdown-alert-caution
+{
 	padding: 0.4em 0.6em;
 	border-radius: 0 0.2em 0.2em 0;
 }
+.markdown-alert-note::before,
 .note::before		{ color: #31a0fc; content: "\0024d8\0000a0Note"; }
+.markdown-alert-tip::before,
 .tip::before		{ color: #25cb1c; content: "\01f4a1\0000a0Tip"; }
-.important::before	{ color: #911ccb; content: "\01f53a\0000a0Important"; }
+.markdown-alert-important::before,
+.important::before	{ color: #911ccb; content: "\01f7e3\0000a0Important"; }
+.markdown-alert-warning::before,
 .warning::before	{ color: #e0b840; content: "\0026a0\0000a0Warning"; }
+.markdown-alert-caution::before,
 .caution::before	{ color: #e04040; content: "\00203c\0000a0Caution"; }
+
+.markdown-alert-note::before,
+.markdown-alert-tip::before,
+.markdown-alert-important::before,
+.markdown-alert-warning::before,
+.markdown-alert-caution::before,
 .note::before, .tip::before, .important::before, .warning::before, .caution::before {
 	display: block;
 	font-weight: bold;
 	margin-bottom: 0.3em;
 }
+.markdown-alert-note,
 .note		{ border-left: 0.2em solid #31a0fc; background: #31a1fc1f; }
+.markdown-alert-tip,
 .tip		{ border-left: 0.2em solid #25cb1c; background: #31fc491f; }
+.markdown-alert-important,
 .important	{ border-left: 0.2em solid #911ccb; background: #bc31fc1f; }
+.markdown-alert-warning,
 .warning	{ border-left: 0.2em solid #e0b840; background: #efc7461f; }
+.markdown-alert-caution,
 .caution	{ border-left: 0.2em solid #e04040; background: #ef5f461f; }
 
+/* markdown-it-alert-title. We *should* use their provided styles really.... but meh */
+.markdown-alert-title { display: none; }
 
 .contributor-list {
 	list-style-type: none;

.docs/lib/parse_sections.js

@@ -21,6 +21,9 @@ markdown.use(markdown_prism, {
 	}
 });
 
+const alerts = require("markdown-it-github-alerts");
+markdown.use(alerts);
+
 function extract_title(line) {
 	return line.match(/#+\s+(.+)\s*/)[1].replace(/^`*|`*$/g, "")
 }

.docs/package.json

@@ -28,6 +28,7 @@
 		"html-entities": "^2.4.0",
 		"html-minifier-terser": "^7.0.0-beta.0",
 		"imagickal": "^5.0.1",
+		"markdown-it-github-alerts": "^0.1.2",
 		"markdown-it-prism": "^2.3.0",
 		"p-memoize": "^7.1.1",
 		"p-queue": "^7.3.4",