new icon: r (original, plain) (#491)

* new icon:r (original, plain)
* fix icon centering

Author: jakob-r

devicon.json

@@ -2338,6 +2338,25 @@
         "color": "#ffd845",
         "aliases": []
     },
+    {
+        "name": "r",
+        "tags": [
+            "programming",
+            "language"
+        ],
+        "versions": {
+            "svg": [
+                "original",
+                "plain"
+            ],
+            "font": [
+                "original",
+                "plain"
+            ]
+        },
+        "color": "#2369bc",
+        "aliases": []
+    },
     {
         "name": "rails",
         "tags": [