Use new typst rendering in /test endpoint

showbits-thermal-printer/src/documents/lib.typ

@@ -0,0 +1,21 @@
+#let init(it) = {
+  set page(
+    width: 384pt,
+    height: auto,
+    margin: (x: 0pt, y: 4pt),
+  )
+  set text(
+    font: ("Unifont", "Unifont-JP", "Unifont Upper"),
+    size: 16pt,
+    fallback: false,
+  )
+  set par(
+    leading: 8pt, // Between lines
+    spacing: 26pt, // Between paragraphs
+  )
+  it
+}
+
+// Determined by experiments so that the top and bottom white border are roughly
+// the same size after tearing off the paper.
+#let feed = v(64pt + 32pt)