Merge pull request #1955 from dariakiseleva/new-icon-mattermost

new icon: Mattermost (original, original-wordmark)

devicon.json

@@ -6508,6 +6508,38 @@
         "color": "#11557C",
         "aliases": []
     },
+    {
+        "name": "mattermost",
+        "altnames": [],
+        "tags": [
+            "app",
+            "chat",
+            "collaboration",
+            "open-source",
+            "platform"
+        ],
+        "versions": {
+            "svg": [
+                "original",
+                "original-wordmark"
+            ],
+            "font": [
+                "original",
+                "original-wordmark"
+            ]
+        },
+        "color": "#19191c",
+        "aliases": [
+            {
+                "base": "original",
+                "alias": "plain"
+            },
+            {
+                "base": "original-wordmark",
+                "alias": "plain-wordmark"
+            }
+        ]
+    },
     {
         "name": "maven",
         "altnames": [