adding slack logo #3020. love slack!

css/font-awesome.css

@@ -1332,3 +1332,6 @@
 .fa-space-shuttle:before {
   content: "\f197";
 }
+.fa-slack:before {
+  content: "\f198";
+}

css/font-awesome.min.css

@@ -1332,3 +1332,6 @@
 .fa-space-shuttle:before {
   content: "\f197";
 }
+.fa-slack:before {
+  content: "\f198";
+}

less/icons.less

@@ -411,3 +411,4 @@
 .@{fa-css-prefix}-try:before { content: @fa-var-try; }
 .@{fa-css-prefix}-plus-square-o:before { content: @fa-var-plus-square-o; }
 .@{fa-css-prefix}-space-shuttle:before { content: @fa-var-space-shuttle; }
+.@{fa-css-prefix}-slack:before { content: @fa-var-slack; }

less/variables.less

@@ -379,4 +379,5 @@
 @fa-var-try: "\f195";
 @fa-var-plus-square-o: "\f196";
 @fa-var-space-shuttle: "\f197";
+@fa-var-slack: "\f198";
 

scss/_icons.scss

@@ -411,3 +411,4 @@
 .#{$fa-css-prefix}-try:before { content: $fa-var-try; }
 .#{$fa-css-prefix}-plus-square-o:before { content: $fa-var-plus-square-o; }
 .#{$fa-css-prefix}-space-shuttle:before { content: $fa-var-space-shuttle; }
+.#{$fa-css-prefix}-slack:before { content: $fa-var-slack; }

scss/_variables.scss

@@ -379,4 +379,5 @@ $fa-var-vimeo-square: "\f194";
 $fa-var-try: "\f195";
 $fa-var-plus-square-o: "\f196";
 $fa-var-space-shuttle: "\f197";
+$fa-var-slack: "\f198";
 

src/icons.yml

@@ -2718,3 +2718,10 @@ icons:
     created:    4.1
     categories:
       - Web Application Icons
+
+  - name:       Slack Logo
+    id:         slack
+    unicode:    f198
+    created:    4.1
+    categories:
+      - Brand Icons