docs: add example categories

Assisted-by: Delta:zai-glm-5.3

site/calepin.toml

@@ -15,3 +15,11 @@ title = "Start"
   [[sidebar.section.item]]
   target = "index.typ"
 
+[[sidebar.section]]
+title = "Categories"
+  [[sidebar.section.item]]
+  target = "thermo/index.typ"
+  [[sidebar.section.item]]
+  target = "security/index.typ"
+  [[sidebar.section.item]]
+  target = "homelab/index.typ"

site/homelab/index.typ

@@ -0,0 +1,4 @@
+#import "@preview/calepin:0.1.7": *
+#show: page-layout.with(title: "Homelab")
+
+= Homelab

site/security/index.typ

@@ -0,0 +1,4 @@
+#import "@preview/calepin:0.1.7": *
+#show: page-layout.with(title: "Security")
+
+= Security

site/thermo/index.typ

@@ -0,0 +1,4 @@
+#import "@preview/calepin:0.1.7": *
+#show: page-layout.with(title: "Thermodynamics")
+
+= Thermodynamics