Update webpack config

- write bundle to `/build`
- add support for SASS
- improve options view as a proof o concept for styling

src/css/_mixins.scss

@@ -0,0 +1,63 @@
+$spacer: 1rem !default;
+$spacers: (
+  0: 0,
+  1: (
+    $spacer * 0.25
+  ),
+  2: (
+    $spacer * 0.5
+  ),
+  3: $spacer,
+  4: (
+    $spacer * 1.5
+  ),
+  5: (
+    $spacer * 3
+  )
+);
+
+@each $prop, $abbrev in (margin: m, padding: p) {
+  @each $size, $length in $spacers {
+    .#{$abbrev}-#{$size} {
+      #{$prop}: $length !important;
+    }
+    .#{$abbrev}t-#{$size},
+    .#{$abbrev}y-#{$size} {
+      #{$prop}-top: $length !important;
+    }
+    .#{$abbrev}r-#{$size},
+    .#{$abbrev}x-#{$size} {
+      #{$prop}-right: $length !important;
+    }
+    .#{$abbrev}b-#{$size},
+    .#{$abbrev}y-#{$size} {
+      #{$prop}-bottom: $length !important;
+    }
+    .#{$abbrev}l-#{$size},
+    .#{$abbrev}x-#{$size} {
+      #{$prop}-left: $length !important;
+    }
+  }
+}
+
+@each $size, $length in $spacers {
+  .m-auto {
+    margin: auto !important;
+  }
+  .mt-auto,
+  .my-auto {
+    margin-top: auto !important;
+  }
+  .mr-auto,
+  .mx-auto {
+    margin-right: auto !important;
+  }
+  .mb-auto,
+  .my-auto {
+    margin-bottom: auto !important;
+  }
+  .ml-auto,
+  .mx-auto {
+    margin-left: auto !important;
+  }
+}