feat(main): Add base theme: This is the falcon theme out of the box.

This is falcon v3.1.2

falcon/_dev/css/theme/components/alert-toast/_alert-toast-stack.scss

@@ -0,0 +1,11 @@
+@use 'sass:map';
+
+
+.alert-toast-stack {
+  position: fixed;
+  right: map.get($spacers, 3);
+  top: map.get($spacers, 3);
+  width: rem-calc(250px);
+  display: block;
+  z-index: 101;
+}

falcon/_dev/css/theme/components/alert-toast/_alert-toast.scss

@@ -0,0 +1,43 @@
+@use "sass:map";
+
+.alert-toast {
+  $self: &;
+
+  @include font-size($font-size-sm);
+  margin-bottom: map.get($spacers, 3);
+  opacity: 0;
+  transform: translateX(100%);
+  box-shadow: $box-shadow;
+  border-radius: $border-radius;
+  transition: 0.4s ease-in-out;
+
+  &__content {
+    padding: map.get($spacers, 2) map.get($spacers, 3);
+  }
+
+  &.show {
+    opacity: 1;
+    transform: translateX(0);
+  }
+
+  &--info {
+    color: color-yiq($primary);
+    background: $primary;
+  }
+
+  &--danger {
+    color: color-yiq($danger);
+    background: $danger;
+  }
+
+  &--warning {
+    color: color-yiq($warning);
+    background: $warning;
+  }
+
+  &--success {
+    color: color-yiq($success);
+    background: $success;
+  }
+}
+

falcon/_dev/css/theme/components/alert-toast/_index.scss

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+@import "alert-toast-stack";
+@import "alert-toast";