feat(icons): add layout-freeform (#4543)

* feat(icons): add layout-freeform

Adds an icon for freeform layout: three blocks, no two sharing an edge.
It matches the "no auto layout" / free positioning mode found in design
tools, as the counterpart to constrained layout modes.

Design notes:
- Reuses the 7x7 rx=1 block already shared by layout-grid, layout-list
  and layout-panel-*, rather than introducing a new base shape.
- Each block is offset so that no two share an edge, which is what
  separates it from layout-grid.
- The offset is 1px: a 2px offset reads more clearly at 16px, but brings
  the top-right and bottom-left blocks within 1.66px of each other
  diagonally, under the 2px element spacing guideline. See the PR for the
  alternatives.

* Update icons/layout-freeform.json

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

---------

Co-authored-by: Eric Fennis <eric.fennis@gmail.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

icons/layout-freeform.json

@@ -0,0 +1,31 @@
+{
+  "$schema": "../icon.schema.json",
+  "contributors": [
+    "samuelalake"
+  ],
+  "use-cases": [
+    "turning off auto layout in a design inspector",
+    "switching a dashboard section to free drag-and-drop placement",
+    "selecting freeform arrangement in a page builder",
+    "indicating unstructured layout mode in a whiteboard or canvas app",
+    "representing elements not aligned to a grid"
+  ],
+  "tags": [
+    "layout",
+    "freeform",
+    "free",
+    "absolute",
+    "position",
+    "auto layout",
+    "unaligned",
+    "scattered",
+    "arrange",
+    "blocks",
+    "canvas",
+    "frame"
+  ],
+  "categories": [
+    "design",
+    "layout"
+  ]
+}

icons/layout-freeform.svg

@@ -0,0 +1,15 @@
+<svg
+  xmlns="http://www.w3.org/2000/svg"
+  width="24"
+  height="24"
+  viewBox="0 0 24 24"
+  fill="none"
+  stroke="currentColor"
+  stroke-width="2"
+  stroke-linecap="round"
+  stroke-linejoin="round"
+>
+  <rect width="7" height="7" x="3" y="3" rx="1" />
+  <rect width="7" height="7" x="14" y="4" rx="1" />
+  <rect width="7" height="7" x="4" y="14" rx="1" />
+</svg>