Add Cash App icon (#1007)

* Add Cash App icon SVG

* Add Cash App logo details

The logo consists of a gradient from #00C244 to #00D64B. I opted for the
former (which is a bit darker) as their interfaces tend to use darker
shades of green as well.

_data/simple-icons.json

@@ -290,6 +290,11 @@
             "hex": "509CF6",
             "source": "https://www.campaignmonitor.com/brand"
         },
+        {
+            "title": "Cash App",
+            "hex": "00C244",
+            "source": "https://cash.app/press"
+        },
         {
             "title": "Castorama",
             "hex": "0078D7",

icons/cashapp.svg

@@ -0,0 +1 @@
+<svg aria-labelledby="simpleicons-cashapp-icon" role="img" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title id="simpleicons-cashapp-icon">Cash App icon</title><path d="M23.59 3.47A5.1 5.1 0 0 0 20.54.42C19.23 0 18.04 0 15.62 0H8.36c-2.4 0-3.61 0-4.9.4A5.1 5.1 0 0 0 .41 3.46C0 4.76 0 5.96 0 8.36v7.27c0 2.41 0 3.6.4 4.9a5.1 5.1 0 0 0 3.05 3.05c1.3.41 2.5.41 4.9.41h7.28c2.41 0 3.61 0 4.9-.4a5.1 5.1 0 0 0 3.06-3.06c.41-1.3.41-2.5.41-4.9V8.38c0-2.41 0-3.61-.41-4.91zM17.42 8.1l-.93.93a.5.5 0 0 1-.67.01 5 5 0 0 0-3.22-1.18c-.97 0-1.94.32-1.94 1.21 0 .9 1.04 1.2 2.24 1.65 2.1.7 3.84 1.58 3.84 3.64 0 2.24-1.74 3.78-4.58 3.95l-.26 1.2a.49.49 0 0 1-.48.39H9.63l-.09-.01a.5.5 0 0 1-.38-.59l.28-1.27a6.54 6.54 0 0 1-2.88-1.57v-.01a.48.48 0 0 1 0-.68l1-.97a.49.49 0 0 1 .67 0c.91.86 2.13 1.34 3.39 1.32 1.3 0 2.17-.55 2.17-1.42 0-.87-.88-1.1-2.54-1.72-1.76-.63-3.43-1.52-3.43-3.6 0-2.42 2.01-3.6 4.39-3.71l.25-1.23a.48.48 0 0 1 .48-.38h1.78l.1.01c.26.06.43.31.37.57l-.27 1.37c.9.3 1.75.77 2.48 1.39l.02.02c.19.2.19.5 0 .68z"/></svg>