add skeleton and first modifications

vendor/font-awesome/less/list.less

+// List Icons
+// -------------------------
+
+.@{fa-css-prefix}-ul {
+  padding-left: 0;
+  margin-left: @fa-li-width;
+  list-style-type: none;
+  > li { position: relative; }
+}
+.@{fa-css-prefix}-li {
+  position: absolute;
+  left: -@fa-li-width;
+  width: @fa-li-width;
+  top: (2em / 14);
+  text-align: center;
+  &.@{fa-css-prefix}-lg {
+    left: (-@fa-li-width + (4em / 14));
+  }
+}

vendor/font-awesome/less/mixins.less

+// Mixins
+// --------------------------
+
+.fa-icon() {
+  display: inline-block;
+  font: normal normal normal @fa-font-size-base/@fa-line-height-base FontAwesome; // shortening font declaration
+  font-size: inherit; // can't have font-size inherit on line above, so need to override
+  text-rendering: auto; // optimizelegibility throws things off #1094
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+
+}
+
+.fa-icon-rotate(@degrees, @rotation) {
+  -ms-filter: "progid:DXImageTransform.Microsoft.BasicImage(rotation=@{rotation})";
+  -webkit-transform: rotate(@degrees);
+      -ms-transform: rotate(@degrees);
+          transform: rotate(@degrees);
+}
+
+.fa-icon-flip(@horiz, @vert, @rotation) {
+  -ms-filter: "progid:DXImageTransform.Microsoft.BasicImage(rotation=@{rotation}, mirror=1)";
+  -webkit-transform: scale(@horiz, @vert);
+      -ms-transform: scale(@horiz, @vert);
+          transform: scale(@horiz, @vert);
+}
+
+
+// Only display content to screen readers. A la Bootstrap 4.
+//
+// See: http://a11yproject.com/posts/how-to-hide-content/
+
+.sr-only() {
+  position: absolute;
+  width: 1px;
+  height: 1px;
+  padding: 0;
+  margin: -1px;
+  overflow: hidden;
+  clip: rect(0,0,0,0);
+  border: 0;
+}
+
+// Use in conjunction with .sr-only to only display content when it's focused.
+//
+// Useful for "Skip to main content" links; see http://www.w3.org/TR/2013/NOTE-WCAG20-TECHS-20130905/G1
+//
+// Credit: HTML5 Boilerplate
+
+.sr-only-focusable() {
+  &:active,
+  &:focus {
+    position: static;
+    width: auto;
+    height: auto;
+    margin: 0;
+    overflow: visible;
+    clip: auto;
+  }
+}

vendor/font-awesome/less/screen-reader.less

+// Screen Readers
+// -------------------------
+
+.sr-only { .sr-only(); }
+.sr-only-focusable { .sr-only-focusable(); }

vendor/font-awesome/scss/_fixed-width.scss

+// Fixed Width Icons
+// -------------------------
+.#{$fa-css-prefix}-fw {
+  width: (18em / 14);
+  text-align: center;
+}