Add ligature icon (#1160)

* Add `ligature` icon

* Refine `ligature` icon

* Fix missing serifs

icons/ligature.json

@@ -0,0 +1,13 @@
+{
+  "$schema": "../icon.schema.json",
+  "tags": [
+    "text",
+    "font",
+    "typography",
+    "alternates",
+    "alternatives"
+  ],
+  "categories": [
+    "text"
+  ]
+}

icons/ligature.svg

@@ -0,0 +1,17 @@
+<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="M8 20V8c0-2.2 1.8-4 4-4 1.5 0 2.8.8 3.5 2" />
+  <path d="M6 12h4" />
+  <path d="M14 12h2v8" />
+  <path d="M6 20h4" />
+  <path d="M14 20h4" />
+</svg>