feat(icons): added opacity icon (#4222)

* Added icons/opacity.svg

* Added icons/opacity.json

* Updated icons/opacity.svg

* Updated icons/opacity.json

* Adjust usecases

---------

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

icons/opacity.json

@@ -0,0 +1,32 @@
+{
+  "$schema": "../icon.schema.json",
+  "contributors": [
+    "ilyavred",
+    "jamiemlaw"
+  ],
+  "use-cases": [
+    "Setting the opacity of layers or objects in graphic editors",
+    "Adjusting the opacity of fills, strokes, or other object attributes",
+    "Adjusting the alpha channel in color pickers",
+    "Indicating that a layer or element is semi-transparent"
+  ],
+  "tags": [
+    "opacity",
+    "opaque",
+    "transparency",
+    "visibility",
+    "fade",
+    "lens",
+    "glass",
+    "blur",
+    "filter",
+    "clear",
+    "mask",
+    "cover",
+    "gradient"
+  ],
+  "categories": [
+    "design",
+    "photography"
+  ]
+}

icons/opacity.svg

@@ -0,0 +1,25 @@
+<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="M12 3h.01" />
+  <path d="M12 9h.01" />
+  <path d="M15 6h.01" />
+  <path d="M18 3h.01" />
+  <path d="M21 6v13a2 2 0 0 1-2 2H6" />
+  <path d="M3 12h.01" />
+  <path d="M3 18h.01" />
+  <path d="M3 6h.01" />
+  <path d="M6 15h.01" />
+  <path d="M6 3h.01" />
+  <path d="M6 9h.01" />
+  <path d="M9 12h.01" />
+  <path d="M9 6h.01" />
+</svg>