feat(icons): add angle (#4545)

* feat(icons): add angle

Adds an angle icon: two rays meeting at a vertex with an arc marking the
angle between them. There is no icon for an angle or degree measurement
in the set today.

The arc is r=10 centred on the vertex at (3,21), so its endpoints land
exactly on the two rays rather than floating near them. The rays reuse
the 2px rounded corner used throughout the set.

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

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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/angle.json

@@ -0,0 +1,34 @@
+{
+  "$schema": "../icon.schema.json",
+  "contributors": [
+    "samuelalake"
+  ],
+  "use-cases": [
+    "rotation input in a design inspector",
+    "measurement tool in cad software",
+    "dimensioning in technical drawings",
+    "labeling angles in geometry exercises",
+    "displaying degrees for rotation controls"
+  ],
+  "tags": [
+    "angle",
+    "degree",
+    "corner",
+    "geometry",
+    "measure",
+    "math",
+    "rotate",
+    "vertex",
+    "slope",
+    "protractor",
+    "measurement",
+    "dimension",
+    "arc",
+    "drafting",
+    "cad"
+  ],
+  "categories": [
+    "math",
+    "design"
+  ]
+}

icons/angle.svg

@@ -0,0 +1,14 @@
+<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"
+>
+  <path d="M3 3v16a2 2 0 0 0 2 2h16" />
+  <path d="M3 11a10 10 0 0 1 10 10" />
+</svg>