Move files to follow webpack structure

src/styles/fa/_icons.scss

@@ -0,0 +1,9 @@
+// specific icon class definition
+// -------------------------
+
+/* Font Awesome uses the Unicode Private Use Area (PUA) to ensure screen
+readers do not read off random characters that represent icons */
+
+@each $name, $icon in $fa-icons {
+  .#{$fa-css-prefix}-#{$name}::before { content: unquote("\"#{ $icon }\""); }
+}