Added Material Design icon. (#1320)

_data/simple-icons.json

@@ -1560,6 +1560,11 @@
             "hex": "3088D4",
             "source": "https://source.joinmastodon.org/mastodon/joinmastodon/blob/master/public/press-kit.zip"
         },
+        {
+            "title": "Material Design",
+            "hex": "757575",
+            "source": "https://material.io/design/"
+        },
         {
             "title": "Mathworks",
             "hex": "0076A8",

icons/materialdesign.svg

@@ -0,0 +1 @@
+<svg role="img" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Material Design icon</title><path d="M12 0C5.377 0 0 5.377 0 12s5.377 12 12 12 12-5.377 12-12S18.623 0 12 0zm0 .75c2.871 0 5.482 1.082 7.469 2.85H4.53A11.197 11.197 0 0 1 12 .75zm-7.186 3.6h14.372L12 18.723 4.814 4.35zM3.6 4.53V19.47A11.197 11.197 0 0 1 .75 12c0-2.87 1.082-5.481 2.85-7.468zm16.8 0A11.197 11.197 0 0 1 23.25 12c0 2.871-1.082 5.482-2.85 7.469V4.53zM4.35 5.1l7.275 14.55H4.35V5.1zm15.3 0v14.55h-7.275L19.651 5.1zM4.533 20.4H19.469A11.197 11.197 0 0 1 12 23.25a11.197 11.197 0 0 1-7.468-2.85z"/></svg>