updating to 4.0

New design with breaking changes, gulp 4, all dependencies updated, dev environment changed, and many more changes

vendor/bootstrap/scss/mixins/_text-emphasis.scss

@@ -0,0 +1,14 @@
+// stylelint-disable declaration-no-important
+
+// Typography
+
+@mixin text-emphasis-variant($parent, $color) {
+  #{$parent} {
+    color: $color !important;
+  }
+  a#{$parent} {
+    @include hover-focus {
+      color: darken($color, $emphasized-link-hover-darken-percentage) !important;
+    }
+  }
+}