feat: Add relative y coordinates

gallery/test_yrel.typ

@@ -0,0 +1,46 @@
+// Demonstrates the `(rel: <number>, to: <anchor>)` shorthand for the `y`
+// parameter (analogous to the existing shorthand for `x`).
+#import "/src/lib.typ": circuit, element, util, wire
+
+#set page(width: auto, height: auto, margin: .5cm)
+
+#circuit({
+  // Anchor block: absolute placement.
+  element.block(
+    x: 0, y: 0, w: 2, h: 1.5,
+    id: "A",
+    fill: util.colors.orange,
+    ports: (east: ((id: "out"),))
+  )
+
+  // X relative, Y absolute (existing feature).
+  element.block(
+    x: (rel: 1, to: "A.east"), y: 0, w: 2, h: 1.5,
+    id: "B",
+    fill: util.colors.yellow,
+    ports: (west: ((id: "in"),), east: ((id: "out"),))
+  )
+
+  // Both X and Y relative to another element's anchor (new feature).
+  element.block(
+    x: (rel: 1, to: "B.east"),
+    y: (rel: 2, to: "B.south-west"),
+    w: 2, h: 1.5,
+    id: "C",
+    fill: util.colors.green,
+    ports: (west: ((id: "in"),))
+  )
+
+  // Y relative only, X absolute.
+  element.block(
+    x: 0,
+    y: (rel: -2.5, to: "A.south-west"),
+    w: 2, h: 1.5,
+    id: "D",
+    fill: util.colors.blue,
+    ports: (east: ((id: "out"),))
+  )
+
+  wire.wire("wAB", ("A-port-out", "B-port-in"))
+  wire.wire("wBC", ("B-port-out", "C-port-in"), style: "zigzag")
+})