Add combine icon (#1069)

Co-authored-by: Eric Fennis <eric.fennis@gmail.com>

icons/combine.json

@@ -0,0 +1,19 @@
+{
+  "$schema": "../icon.schema.json",
+  "tags": [
+    "cubes",
+    "packages",
+    "parts",
+    "units",
+    "collection",
+    "cluster",
+    "combine",
+    "gather",
+    "merge"
+  ],
+  "categories": [
+    "shapes",
+    "development",
+    "files"
+  ]
+}

icons/combine.svg

@@ -0,0 +1,18 @@
+<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="8" height="8" x="2" y="2" rx="2" />
+  <path d="M14 2c1.1 0 2 .9 2 2v4c0 1.1-.9 2-2 2" />
+  <path d="M20 2c1.1 0 2 .9 2 2v4c0 1.1-.9 2-2 2" />
+  <path d="M10 18H5c-1.7 0-3-1.3-3-3v-1" />
+  <polyline points="7 21 10 18 7 15" />
+  <rect width="8" height="8" x="14" y="14" rx="2" />
+</svg>