minor changes to manual for universe publication

manual.typ

@@ -1,7 +1,5 @@
 #import "@preview/tidy:0.4.0"
-
 #import "src/lib.typ"
-
 #import "gallery/readme_banner.typ" as banner
 
 #set document(
@@ -19,6 +17,25 @@
     }
   }
 )
+#set heading(numbering: (..num) => if num.pos().len() < 4 {
+  numbering("1.1", ..num)
+})
+
+#let code-block(code) = {
+  let txt = code.text
+  txt = txt.replace("$version", str(lib.version))
+  return box(
+    raw(
+      txt,
+      lang: code.lang,
+      block: true
+    ),
+    fill: luma(95%),
+    inset: 1em,
+    radius: 0.5em,
+    stroke: luma(80%) + 0.5pt
+  )
+}
 
 #align(center)[
   #v(1cm)
@@ -52,13 +69,33 @@
   inset: 1em,
   outline(
     indent: 1em,
-    target: heading.where(level: 2)
+    depth: 2
   )
 )
 
-
 #pagebreak(weak: true)
 
+= Introduction
+
+This package provides several common hashing algorithms and other related functions. All functions are directly available in the package's namespace (i.e. no need to import sub-modules).
+
+To use it, you can simply import the package as a whole:\
+#pad(left: 1em, code-block(```typ
+#import "@preview/jumble:$version"
+...
+#jumble.md5(msg)
+```))
+or import specific functions (or all):\
+#pad(left: 1em, code-block(```typ
+#import "@preview/jumble:$version": md5
+...
+#md5(msg)
+```))
+
+#pagebreak(weak: true)
+
+= Reference
+
 #let mod = tidy.parse-module.with(
   scope: (jumble: lib),
   preamble: "#import jumble: *;"
@@ -66,7 +103,7 @@
 
 #let sha-doc = mod(
   read("src/sha.typ"),
-  name: "sha"
+  name: "SHA"
 )
 #tidy.show-module(sha-doc)
 
@@ -74,7 +111,7 @@
 
 #let md-doc = mod(
   read("src/md.typ"),
-  name: "md"
+  name: "MD"
 )
 #tidy.show-module(md-doc)