Add Unix icon (#659)

Co-authored-by: Clemens Bastian <8781699+amacado@users.noreply.github.com>

Author: cseelus

devicon.json

@@ -3621,6 +3621,22 @@
         "color": "#dd4814",
         "aliases": []
     },
+    {
+        "name": "unix",
+        "tags": [
+            "os"
+        ],
+        "versions": {
+            "svg": [
+                "original"
+            ],
+            "font": [
+                "original"
+            ]
+        },
+        "color": "#4051b5",
+        "aliases": []
+    },
     {
         "name": "uwsgi",
         "tags": [